Most people acquiring hearing aids report trouble hearing speech, or more often trouble hearing speech in noise. Here speech testing becomes a strong test tool in the assessment of the problem the patient faces. Speech audiometry employs speech signals and can be used to examine the processing ability and if it is affected by disorders of the middle ear, cochlea, auditory nerve, brainstem pathway, and auditory centers of the cortex.
There is a variety of tests available with speech testing with the basic speech audiometry being an assessment of the reception, discrimination and recognition of speech. Reception refers to the level at which the patient can hear speech is present, discrimination refers to the level at which the patient can discriminate between words, while recognition refers to the level at which the patient can recognize and recall the word.
More advanced speech testing takes into account how speech is understood in the presence of noise, with various noise types such as white noise, speech noise, babble noise, or running speech as noise source and provide information about the signal-to-noise ratio (SNR) at which the patient can understand speech. Other components such as the placement of the speech signal in relation to the noise source and the tonal differences between the speech signal and the masking signal, is some of the things incorporated into more advance speech testing.
Speech Detection Threshold (SDT)
Speech detection threshold (SDT) refers to the level at which the patient can hear speech is present in 50% of the cases.
The speech detection threshold can be used as a cross-check of the air conduction audiometry and should closely agree with the PTA (Pure Tone Average). The PTA can be calculated in different ways but is usually the average of thresholds obtained at 500, 1000, and 2000 Hz. It is generally accepted that if the PTA and the SRT is within ± 6 dB of each other the accordance is good, if it is ±7 to 12 dB it is adequate, and if it is ±13 or more, it is poor.
Note: Speech detection threshold is sometimes referred to as speech reception threshold abbreviated - SRT, not to be confused with speech recognition threshold, abbreviated - SRT. For that matter the term speech detection threshold is used and abbreviated – SDT.
Speech Recognition Threshold (SRT)
The SRT examines at which level 50% of the speech material (usually numbers or spondaic words) is repeated correctly.
In addition, SRT gives an index of the hearing sensitivity of speech and helps determine the starting point for other supra-threshold measures such as WR (Word Recognition).
Word Recognition Score (WR)
WR is sometimes also referred to as SDS (Speech Discrimination Scores) and represents the number of words correctly repeated, expressed as a percentage of correct (discrimination score) or incorrect (discrimination loss). Pressing correct means the word is a 100% correct, while incorrect correspond with 0% correct.
The score can be obtained as a phoneme score that provides information about what phonemes the patient has difficulty hearing at a particular intensity level. This is helpful for counselling and rehabilitation purposes.
Correct / incorrect (discrimination score / discrimination loss)
In the suite. Correct: A mouse click on this button will store the word as correctly repeated. The left arrow key can also be used for storing as correct. Incorrect: A mouse click on this button will store the word as incorrectly repeated. The right arrow key can also be used to score as incorrect. Store: A mouse click on this button will store the speech threshold in the speech graph. A point can also be stored by pressing S.
On the standalone devices. Press incorrect on the keyboard to store the word as incorrect (0%) or press correct on the keyboard to store the word as correct (100%).
When the speech material is indexed according to the number of phonemes in each word, the soft key numbers avialable for scoring will be active.
|e.g. for a word with two phonemes the soft keys 0,1 and 2 will become available for scoring. The upper the display in the suites, while the lower displays the buttons on the standalone audiometer.|
|When the word is scored with the use of phonemes, the number of correct phonemes will appear below the word.|
The percentage will be calculated as the numbers of phonemes correct out of the total number of phonemes that has been presented up until the given word.
|Thereby the storing can be done at any time during the scoring.|
What is required
Before performing speech audiometry you may wish to do the tone audiogram. This provides valuable predictive information useful in the speech testing, including information about when masking is needed during speech testing. For more information about masking please refer to the quick guide ‘Audiometric masking’.
The SRT/WR displayed as a table allows for measuring multiple SRTs using different test parameters, e.g. Transducer, Test Type, Intensity, Masking, and Aided together with the SRT or WR score.
When showing the SRT in graph mode the speech audiogram calculates the SRT value based on the norm curve (the distance in dB from the point where the norm curve crosses 50% to the point where the speech curve crosses 50%) like shown below. The result is then an expression of how much you need to turn up the level compared to normal in order for the patient to be able to repeat 50%.
Use the m-curve for multi syllabic words and the s-curve if using single syllabic words. The curves can be edited according to the normative data you wish to use in the speech settings.
Note that the norm curves change based on the speech material. You must therefore ensure that WR1, WR2 or WR3 is linked to single or multisyllabic words to show the SRT. Calculating the WR SRT is only available when using the suite.
When running the speech test using wavefiles, the tester can decide to present manually, continuously or timeout for the speech setup.
Manual mode allows the tester to manually press the Tone Switch/Enter button to present the word and then score it as Incorrect of Correct before moving on to the next word.
In Continuous mode, the next word will automatically be presented after scoring incorrect or correct. In the Time Out mode, the word played will be scored as either correct or incorrect if no scoring is entered within 1 to 5 seconds.
Speech in Noise
Problems understanding speech in noise is a common complaint from people with hearing loss. Having the ability to test the patient with speech in noise provides useful information about the impact of the hearing loss on the patient’s ability to communicate. It also provides information about whether the patient is actually getting the expected benefit from the hearing aids when communicating in noisy environments.
Testing the patient in a speech in noise setup can be done using a free field setup either by presenting the speech signal and noise signal from the same speaker or alternatively, separating the speech signal and noise signal by presenting the signal from two different speakers. It can be done by presenting the signal and noise to the same ear on the AC40 or by selecting the test speech in noise on the AD629.
If the intention is to present the speech signal to both ears at the same time this is done by selecting the same output for both channels on the AC40. On the AD629 the binaural speech is selected by choosing the test Speech - Ch2on. Note this is only available with the AD629 extended.
Stach, B.A (1998) Clinical Audiology: An introduction, Cengage Learning
Difficulty with hearing in background noise is a common complaint among hearing aid users. Therefore, the measurement of SNR loss (signal-to-noise ratio loss) is important because a person’s ability to understand speech in noise cannot be reliably predicted from the pure tone audiogram. The QuickSIN test was developed to provide a quick estimate of SNR loss. A list of six sentences with five key words per sentence is presented in four-talker babble noise. The sentences are presented at pre-recorded signal-to-noise ratios which decrease in 5-dB steps from 25 (very easy) to 0 (extremely difficult). The SNRs used are: 25, 20, 15, 10, 5 and 0, encompassing normal to severely impaired performance in noise.
The QuickSIN test was developed to
It is possible to do an aided QuickSIN when using the audiometer via Diagnostic Suite, given the audiometer is free field calibrated. Making an Aided QuickSIN and an unaided QuickSIN is a useful tool to evaluate the benefit of a hearing aid treatment in a noisy environment.
Select Free Field as the transducer, this will activate the aided function. Click on the aided button, this will add an extra column to the QuickSIN scoring table allowing you to compare unaided and aided results.
The SNR loss = 25.5 – Total, where the Total score is a sum of the score for each sentence (see example below). The SNR loss is then categorized based on the definition seen in the table in the test screen. Example: The total score is 22, which gives a SNR loss of 3.5. According to the definition the patient is having a Mild SNR loss.
For more information, please refer to Etymotic Research’s QuickSINTM Speech-in-Noise Test manual, version 1.3.
The Stenger test is based on the auditory phenomenon “The Stenger Principle” and is used when a patient is suspected malingering a hearing loss. The Stenger Principle states that only the louder of two similar tones presented to both ears at the same time will be perceived.
Generally, it is recommended only to perform the Stenger test in cases of unilateral hearing losses or significant asymmetries (at least 20dB).
Test Procedure for Speech Stenger
In cases where you detect a symmetrical hearing loss, traditional audiometry without masking is usually sufficient. However, be aware that in cases of asymmetrical hearing loss, one cannot be certain that the intended ear is the one actually detecting the sound.
To prevent this phenomenon causing an erroneous measurement, masking noise can be used to occupy the good ear (non-test ear) while testing the other one (Stach 1998, Katz 2002 and British Society of Audiology 2004). Masking can be applied to air conduction, bone conduction and speech audiometry. The need to mask the better hearing ear is linked to the interaural attenuation, which equals the amount of attenuation the sound is exposed to on its way through the skull.
Even though the interaural attenuation is very individual and varies with frequency it can on average be estimated to a minimum of 40dB for supra-aural headphones and 50dB for inserts. Regarding bone conduction, the interaural attenuation is a minimum of 0dB which means that crossing over of the stimulus may occur at all times, and this is what one should assume.
When measuring an audiogram on a patient with hearing within the normal range on one ear, but a moderate to severe hearing loss on the other, there is a potential risk of the good ear hearing the tone when trying to test the damaged ear. That is, the sound vibration may travel through the head and be heard by the opposite good ear when the vibrations of the signal are of sufficient
magnitude. Therefore, you are actually measuring the thresholds from the wrong ear. This could be the case in the example here and masking is needed in the right ear (better ear) while reassessing the left (poorer ear).
Masking is also needed to differentiate between sensorineural and conductive or mixed hearing losses. In the example, it is unknown if the loss of the left ear is sensorineural, conductive or a mixed hearing loss. The origin will be revealed by obtaining the bone conduction threshold for the left ear while occupying the right ear with masking.
In the example above, channel 2 should be set to Right (non-test ear) using the preferred masking stimulus (usually NB). Ensure that Rev is active to ensure that the masking noise is continuous. Channel 1 should be set to Left (test ear) using the preferred stimulus (usually Tone). The masking frequency will automatically change along with the tone frequency when masking is turned ON. You can set the masking and tone frequencies by using the Frequency Up Down buttons. While trying to establish the true threshold of the left ear, the right ear is now distracted with noise.
When storing a threshold while masking, the final masking level is stored in the masking table under the ear that is being tested. The terms ‘Effective masking’ in this situation refers to the fact that the narrow band noise level was loud enough to effectively mask a pure tone of the indicated level heard by the masked ear.
ABLB (Alternate Binaural Loudness Balancing) is a test to detect perceived loudness differences between the ears designed for people with unilateral hearing loss. It serves as a possible test for recruitment. The test is interpreted by assessing the loudness differences at high intensity levels. If the loudness perception is at the same intensity level for both ears complete recruitment has occurred in the hearing-impaired ear. Decruitment may occur in case of a retro cochlear disorder. In these cases, loudness in the impaired ear increases more slowly that for the normal hearing ear (Stack 1998).
The same tone is presented alternatively to both ears. The intensity is fixed in the impaired ear (20 dB above pure tone threshold). The task of the patient is to adjust the level of the better ear until the signal in the two ears is of equal intensity. Note however that the test may also be performed by fixing the intensity in the normal hearing ear and having the patient set the tone for the impaired ear.
The ABLB results are interpreted based on the laddergram, which displays the difference between the intensities for the right and left ear. The good ear is used as reference and displays the normal dynamic range where no recruitment is present. The poorer ear will display a narrowed dynamic range which indicates a degree of recruitment. In the example above, the left ear is the reference ear relative to the right ear showing a narrowed dynamic range, indicating recruitment in the right ear. If the range of the poorer ear is the same as for the good ear there is no recruitment.
Stach A.A., 1998. Clinical Audiology: An Introduction. Cengage Learning
SISI is designed to test the ability to recognise 1dB increases in intensity during a series of bursts of pure tones presented 20dB above the pure tone threshold for the test frequency. It can be used to differentiate between cochlear and retro cochlear disorders, as a patient with a cochlear disorder will be able to perceive the increments of 1dB, whereas a patient with a retro cochlear disorder will not.
The SISI test should be conducted at 20dB SL for all frequencies tested. If the patient does not manage to get a high score on the SISI test, this could be indicative of retro cochlear damage.
Hughson Westlake is an automatic pure tone test procedure. In this test method, the threshold of hearing is defined as 2 out of 3 (or 3 out of 5) correct responses during the ascending portion of the tone presentation. If the patient responds when the tone is ascending, the test will automatically decrease the level by 10 dB. The patient has to respond to the same intensity 2 out of 3 or 3 out of 5 times for the threshold to be recorded. Intensity increases will be in steps of 5 dB while the intensity decreases will be in steps of 10 dB.
To measure only one frequency, select the desired frequency and then press on the button Single.
To obtain a threshold including the high frequency range press the button High. Note The range is only available if it is selected in the Setup │ Auto settings.
Setup │ Auto settings allows for changing the threshold method 2 out of 3 or 3 out of 5. The frequencies included in the test is selected by ticking of the frequencies.
Békésy is an automatic method of measuring audiometric thresholds. It can be used for audiometric screening or in differentiation between the cause of the hearing loss e.g. non-organic hearing loss (Gelfand, 2009) or the origin of the damage in the ear (conductive, cochlear or retro cochlear) (James Jerger, 1962).
The patient being tested needs to hold down the response button when the tone is heard and release when the tone is no longer heard. When the response button is pressed, the intensity level of the frequency tested will automatically be reduced. When the response button is released, the intensity level will automatically increase. The patient’s response will be recorded as a trace on the Test Screen.
When using the Békesy for clinical purposes, one threshold is obtained with a continuous tone and one with a pulsed tone. The results are interpreted based on the display of the continuous and pulsed tone.
Békésy Type 1: Continuous and pulsed tone overlapped (Cochlear disorder)
Békésy Type 2: Continuous tracing slightly worse than pulsed tone tracing (Cochlear disorder) Békésy Type 3: Continuous drops off the graph as a result of adaptation to the tone (Retro cochlear disorder)
Békésy Type 4: Continuous tracing is 20 dB lower that pulsed tone tracing (Retro cochlear disorder)
Békésy Type 5: Pulsed tone tracing below continuous tracing (feigning hearing loss)
Setup│Auto settings allows for changing the allowed deviation and number of reversals needed for a response to be stored.
Gelfand, S.A. (2009) Essentials of Audiology, Theime.
Jerger, J. (1962) Bekesy Audiometry, Hearing Tests in Otologic Diagnostics, ASHA May.
Masking Level Difference refers to the improvement in detecting a tone or speech in noise when the phase of the tone or the noise is reversed by 180 degrees. It aims to assess central auditory function and is specifically sensitive to brainstem lesions, but peripheral changes (like a hearing loss) may also affect the MLD.
The MLD is a low frequency phenomenon, related to the ability of the auditory system to perceive differences in timing of a sound reaching the two ears. This helps to localise low frequency sounds that reach the ears at different times due to the longer wave length.
The MLD is usually referred to as the difference of improvement in dB between a “homophasic” (in-phase) condition and an “antiphasic” (out of phase) condition. Homophasic means that both the signal and the noise are in phase with each other when reaching the two ears. Antiphasic means that either the signal or the noise (not both) is out of phase with each other when reaching the two ears.
The three test conditions for the MLD are:
S0N0: Signal and Noise are IN PHASE when reaching the two ears (Homophasic condition).
SπN0: Signal is OUT OF PHASE, noise is IN PHASE when reaching the two ears (Antiphasic condition).
S0Nπ: Signal is IN PHASE, noise is OUT OF PHASE when reaching the two ears (Antiphasic condition).
The MLD is measured by presenting a low frequency pulsed tone with simultaneous presentation of the corresponding narrow band noise, starting at an intensity of 60 or 65dB to both ears. The first condition should be to find the threshold for the homophasic condition (referred to as S0N0). The next step is to measure the antiphasic condition, either presenting the tone out of phase or the noise out of phase and the masked threshold is determined again. If the brainstem is functioning normally, there will be an improvement in the masked threshold from the homophasic condition to the antiphasic condition. The condition that will yield the greatest MLD is the SπN0 condition, that is, the condition where the signal is out of phase when reaching the two ears but the noise is still in phase.
The masked threshold for the S0N0 condition is 60dB and we reverse the phase of the signal by 180 degrees the threshold for this phase reversed condition (SπN0) improves to 44dB. Then the masking level difference (MLD) from SoNo to SπN0 is 16dB.
Most research having been done on the MLD indicates that in general, if the MLD is less than 7dB, this will indicate a problem with the brainstem and binaural interaction. There will also be a decrease in the hearing MLD if there is a peripheral hearing loss or if the hearing aid is asymmetrical. A normal result for MLD is usually around 12dB (Brown & Musiek, 2013).
Brown, M., Musiek, F. (2013). The Fundamentals of MLD for Assessing Auditory Function. Hearing Journal
The purpose of this document is to provide a quick guide and an overview on using the Callisto™ system to perform QuickSIN testing.
The QuickSIN test was developed to:
QuickSIN for the AUD440 Module
Press start to begin the first sentence on the selected list. The next sentence will automatically play once you have scored the previous sentence.
Additional QuickSIN features
Adding a fourth column to the SNR loss definitions table:
Aided QuickSIN is possible when selecting the free transducer
To activate Aided QuickSIN:
The purpose of this document is to provide a Quick Guide for instructions on how to administer the TEN test with the AC440 Audiometry module in the Equinox2, Affinity2 and CallistoTM. This Quick Guide is based on a white paper that was written for Interacoustics by Brian C.J. Moore (2009)
What is the TEN test?
The TEN(HL) test was developed to provide clinicians with a quick and easy way to identify cochlear dead regions. The test consists of measuring pure tone thresholds in a special masking noise, called the TEN (Threshold Equalizing Noise).
What is a dead region?
A dead cochlear region is defined as a region of the cochlea where there are no functioning inner hair cells and/or neurons. (Moore, 2001). When a pure-tone signal “falls” into a dead region, it can be heard by neighboring hair cells, if the intensity of the signal is loud enough. This is because the pure tone produces sufficient basilar-membrane vibrations in neighboring areas of the cochlea, where there are surviving IHCs and neurons. This phenomenon is defined as “Off Frequency Listening”. Clinically, this will present as a threshold on the traditional pure tone audiogram, but it may not be the real threshold. It is not possible to use traditional pure tone audiometry to determine if there is a dead region present; the TEN test was developed for this very purpose.
When to do the TEN test?
Characteristics that could indicate the presence of a dead region (from Moore, 2009):
Criteria for diagnosing a dead region (Moore et al) :
A dead region at a particular frequency is indicated when:
A masked threshold is at least 10 dB or more above the level of the TEN
|Note: the TEN test is performed ipsilaterally, meaning that the tone and the noise are presented in the same ear. It can only be conducted with TDH39, DD45 and Insert earphones headphones|
Positive TEN test
A dead region at a particular frequency is indicated when:
A masked threshold is at least 10 dB or more above the level of the TEN
Clinical Value of TEN test
If dead regions are present, this may have important implications for fitting hearing aids and for predicting the likely benefit of hearing aids. When a patient has a dead region, there may be little or no benefit from hearing aid amplification for frequencies well inside the dead region (Moore 2009).
Identifying a cochlear dead region can:
1TEN test requires an additional license
Moore, B. C. J. (2001). "Dead regions in the cochlea: Diagnosis, perceptual consequences, and implications for the fitting of hearing aids," Trends Amplif. 5, 1–34.
Moore, B. C. J. (2009). “Audiometer Implementation of the TEN (HL) Test for Diagnosing Cochlear Dead Regions” . White Paper for Interacoustics.
The purpose of this document is to provide a Quick Guide for instructions on how to administer the Acceptable Noise Level (ANL) test with the AC440 Audiometry module in the Equinox 2.0, Affinity 2.0 and Callisto™.
What is the ANL test?
The ANL Test is a method of determining how much noise the patient is able to tolerate whilst listening to a target signal/speaker (Nabalek et al., 1991). It is used as a predictor for how well a patient will cope with amplification when receiving a hearing aid (Nabalek et al., 2006).
The ANL test is designed to be performed via loudspeaker as it is a free field test. However, it can be configured to perform monaurally via selection of headphones and routing the signal to the relevant ear-side. The Equinox and Affinity systems can perform the test binaurally via the R+L feature.
The ANL Test can use any of the materials you have already ripped into your Interacoustics Suite software.
When should I perform the ANL test?
The ANL test is typically performed before the patient is given any form of amplification as a rehabilitative action for their hearing loss.
MCL High – This is the loudest comfortable level the patient can listen to without any competing noise
MCL Low – This is the lowest comfortable level the patient can listen to without any competing noise
MCL Real – This is the patient most comfortable level without any competing noise
BNL – This is the actual ANL test where the MCL Real is presented and the competing noise is manipulated to find an ANL value
It is not essential to perform MCL High and MCL Low for the ANL test, but these are also good indicators of the patients’ comfortable hearing range.
Instructions for the patient will always be displayed at the bottom of the screen.
Click on the MCL High Icon and click play. This will loop your speech material.
Increase and decrease the stimulus intensity to match the patients loudest MCL.
There will be no other change in the display to represent this, only the level in the MCL High icon box.
The display will change within the icon but also a predicted MCL Real will be generated as a midpoint between the MCL High and MCL Low.
What does my ANL value mean?
On performing the ANL test you will obtain an ANL value (in dB) and a percentage. The percentage gives a likelihood of success with amplification (Nabalek et al., 2006) and the ANL value is the outcome of the following calculation:
ANL = MCL - BNL
For response categories the following outcome criteria was determined as an effect of the Nabalek et al. (2006) investigation into ANL outcomes in relation to amplification:
ANL Score 7 dB or less: These individuals have a great prognosis for regular use and acceptance of hearing aids; may not need as much follow-up counseling and guidance as the average patient.
ANL Score 8-12 dB: These are your more common patients and have a good (8) or bad (12) prognosis for regular use and acceptance of hearing aids. These patients may need more follow-up counseling and are excellent candidates for noise reduction technologies.
ANL Score 13 dB or more: These patients are “at risk” for reduced utilization of hearing aids and may need additional post-fitting counseling, guidance, and require noise reduction technologies.
Nabelek, A.K., Tucker, F.M., & Letowski, T.R. (1991). Toleration of background noises: Relationship with patterns of hearing aid use by elderly persons. Journal of Speech and Hearing Research, 34, 679-685.
Nabelek, A., Freyaldenhoven, M., Tampas, J., & Burchfield, S. (2006). Acceptable noise level as a predictor of hearing aid use. Journal of the American Academy of Audiology, 17(9), 626-639.
This is a test to help identify the adaptation of the auditory system (Carhart, 1957). It involves measuring the perceptual reduction in a continuous tone over time. This can indicate towards a cochlear or neural cause ofdeafness.
The test involves looking at the patient’s response to the onset of a supra-threshold sound and then their continuous response to this as it continues over time. For example, in Meniere’s disease this is detected correctly on onset but rapidly deteriorates due to dysfunctional hair cells (Carhart, 1957). A normal response should be maintained for a minute of stimulation. Should a patient not be able to maintain this, the stimulus intensity is increased until a minute is achieved. This is only increased up to a maximum 30dB suprathreshold.
The tone decay can be run on the AC40 as standalone or by using the AC40 with Diagnostic Suite.
High frequency audiometry (above 8 kHz) is performed using the same procedure as normal air conduction audiometry. High frequency audiometry is helpful when testing hearing impairments caused by ototoxicity, noise exposure, and acoustic traumas or in the assessment of patients with tinnitus. The frequency area is more susceptible to the effects of external factors such as medication and loud noises relative to the low and mid frequencies.
Note: High frequency audiometry is only available if the optional high frequency license is installed on the instrument. If the license is not installed or if the headset is not calibrated for high frequencies the HF phone button does not appear on the audiometer and the HF button and HFz button will be dimmed in Diagnostic Suite.
The purpose of tone audiometry is to establish the hearing sensitivity at various frequencies for air conduction and bone conduction. The test can specify the air conduction and bone conduction loss and distinguish between abnormality in the conductive mechanism and sensor neural mechanism. Masking can be applied to both the air conduction and bone conduction threshold to establish pure tone thresholds.
Starting up the Tone Audiometry
For a more detailed description on how to use the stand-alone audiometer, please refer to the relevant Instructions for Use.
Tone audiometry in Diagnostic suite
Starting up the AC440 Module
Presenting the stimuli:
If masking is necessary:
It is possible to define the output of channels for each protocol from the protocol settings.
Interacoustics auto masking is available to ease the effort required in order to mask with correct masking levels. When auto masking is enabled, channel 2 is controlled by the system and is set to the appropriate intensity level.
Auto masking is activated by selecting the icon that shows the mask with letter A.
Green indicates that masking is correctly applied.
Amber indicates that masking is recommended louder and that extended range needs to be activated to allow setting channel 2 to the correct level.
Purple indicates that masking would be needed, but is not possible practically.
Note: The auto masking feature is only available in the Diagnostic Suite – and not on the audiometer as a standalone.
Be aware that patients require proper instructions before audiometry with masking is undertaken. The switching on and off of the masking noise may be uncomfortable to some patients and cause them to become more fatigued. In some cases (when testing young children, some elderly patients or difficult to test patients), it is recommended not to use masking because confusion about the application of masking noise may lead to false responses.
When measuring the second test ear, more information becomes available and it is not guaranteed that the earlier measurements are still correct. By measuring the best ear first and completing air conduction on both ears before measuring bone conduction, most errors can be avoided.
Be careful when storing thresholds where masking was not possible. Masking not possible means that the risk for crossover hearing is high. In these cases it is recommended to store a no-response at the loudest intensity where masking was still possible (by pressing the N key).
The masking help calculates answers to the following questions:
|AC||AC test ear|
|BC||BC test ear|
|IaA||Minimum interaural attenuation|
|IaAc||Minimum interaural attenuation contra transducer|
|Dial||Dial setting test ear|
|Dialc||Dial setting contra (masking level)|
Is masking required?
Masking is recommended when the presentation at the test ear can be heard by at the contralateral side, or in a formula:
Dial – IaA ≥ lowest of ACc and BCc
Is the masking level too low?
The applied masking level is too low when the applied masking level does not match the intensity at which the test signal is heard in the contralateral ear, or in a formula:
Dialc – (ACc – BCc) < Dial – IaA
Is the masking level too high?
The applied masking level is too high when the masking level is so loud that it potentially is heard by the test ear, or in a formula:
|Dialc – IaAc ≥ Dial – (AC – BC)||when testing air conduction|
|Dialc – IaAc ≥ Dial||when testing bone conduction|
Is masking impossible?
Masking is not possible when the needed masking level results in overmasking at the same time:
|Dial + (ACc – BCc) – IaA ≥ Dial – (AC – BC) + IaAc||when testing air conduction|
|Dial + (ACc – BCc) – IaA ≥ Dial + IaAc||when testing bone conduction|
or when the needed masking level is higher than the maximum level of the masking transducer:
Dial + (ACc – BCc) – IaA > maximum available Dialc
Recommended masking intensity
The masking help can indicate a recommended masking intensity. If masking is indeed required and also possible, the recommended masking intensity is given by the minimum required masking level plus a fixed preferred amount:
Recommended Dialc = Dial – IaA + (ACc – BCc) + preferred additional amount.
The recommended masking level is adjusted for values that cannot be reached by the masking transducer due to maximum values.
When the auto masking feature is used, masking intensities are set to the recommended intensity.
Of course if “extended range” is not switched on, the masking intensities are thereby limited accordingly.
Frequency specific inter-aural attenuation
The inter-aural attenuations used by the masking help are frequency specific and can be customized in the setup. The following table shows the default inter-aural attenuation values (IaA). These are partly based on recommendations from the Handbook of Clinical Audiology and are otherwise slightly more conservative then recent publications and will therefore allow for appropriate decision making.
|IaA Headphones (dB)||35||40||40||40||40||40||40||45||50||50||50|
IaA Inserts (dB)
Experienced audiologists are recommended not to use the option of viewing a suggested masking level.
The masking help indicates if masking is performed correctly with the information given at the time of the measurement. When measuring the second ear, more information becomes available and it is not guaranteed that the earlier measurements are still correct. By measuring the best ear first and completing air conduction on both ears before measuring bone conduction, most errors can be avoided.
Although clinicians do often not apply masking for bone conduction in the instance where the air-bone gap is less than 15dB in the better ear, it can be recommended to apply masking to make the measure ear specific. Despite that an experienced clinician would disagree, the masking will, in these cases recommend, that masking is needed. This figure illustrates such a situation.
The Weber test distinguishes between conductive and sensor neural hearing loss through use of a bone conductor. Use the indications to show where the tone is perceived.
If the patient hears the tone better in the poorer ear, the hearing loss is conductive. If the tone is heard better in the better ear, the hearing loss is sensor neural at the given frequency.
Pediatric noise is a special noise stimuli that can be used as an alternative for pure tones, warble tones and narrow band noise. The use of pediatric noise is useful during sound field testing and visual reinforcement audiometry (VRA) as it helps to avoid standing waves as well as maintain the child’s interest during testing. In additional it is useful in other assessments, which requires narrow band noise such as pitch matching and minimum masking level.
Pediatric noise addresses the two problems related to the use of narrow band noise.
1. Pediatric noise is calibrated in dB Hearing Level.
In comparison, the narrow band noise is calibrated for effective masking of tonal sounds of the same dial setting. Practically speaking it means that the narrow band noise is a few dB louder than what is required for threshold measurements.
2. The shape of pediatric noise makes it frequency specific.
While the plateau of the pediatric noise and narrow band noise are of the same width, the pediatric noise has very steep slopes, 100dB/octave vs. 12dB/octave respectively. In case of sloping hearing losses, the use of pediatric noise will not result in off-frequency listening.
Below graph illustrates the shape of the pediatric noise at 1000Hz.
How to select pediatric noise
Ped noise can be run ad stand-alone on the audiometer or via Diagnostic Suite.
On the standalone device, press Tests and use the wheel to select PED: pediatric noise.
When in the PED test screen, the channel 1 Warble button will flash slowly, to indicate that the stimulus used is the pediatric noise. While using this protocol, the audiometer allows toggling from pediatric noise to tone, warble tone and back to pediatric noise.
Note: If operated through Diagnostic Suite, pediatric noise (PED) will be available from the main tone screen in the selection of input.
Conduct threshold evaluation using the pediatric noise for the desired audiometric evaluation method.
Interacoustics masking help is available to make it easier to decide on a safe and correct masking intensity. When masking help is activated, a status light on channel 2 indicates if masking is applied correctly.
Masking help is activated by selecting the icon with the mask.
Grey indicates that the masking help is not active. Green indicates that masking is correctly applied.
Optionally, the masking help can give a suggested masking level. The example here shows that 85 dB, but also 75dB is within the safe masking range.
Amber indicates that masking is recommended differently. There is either too much or too little masking.
Purple indicates that masking would be recommended, but is not practically possible.
Note: The masking feature is only available in the Diagnostic Suite – and not on the audiometer as a standalone.
Because several masking intensities will usually be correct, experienced audiologists are recommended to use the masking help without displaying the recommended masking level.
When measuring the second ear, more information becomes available and it is not guaranteed that the earlier measurements are still correct. By measuring the best ear first and completing air conduction on both ears before measuring bone conduction, most errors can be avoided.
Clinicians do often not apply masking for bone conduction in the instance where the air-bone gap is less than 10dB in the better ear. Against general practice, masking help will always recommend that masking is needed in these cases.
The purpose of this document is to provide a quick guide for basic functions of the AC440 Audiometry modules for the Affinity 2.0/Equinox 2.0 and Callisto™ suites. This Quick Guide will focus on Tone Audiometry as well as a basic introduction to the various icons, tools and menus available.
Starting up the AC440 Module
Conducting Tone Audiometry
Navigation: Tools and functions
For a more detailed description of how to use the AUD440 module, please refer to the following documents:
1 For more information on the Automasking/Masking Help, please refer to the Quick Guide, available on www.interacoustics.com