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Basics

This is an introduction to understanding and reporting on tympanometry measurements.

You should use this guide in conjunction with your own clinic’s protocols and current research in acoustic immittance testing.

Contents:

  1. What is tympanometry?
  2. What is a tympanogram?
  3. Terminology
  4. Tympanogram types
  5. Reasons for repeating tympanometry
  6. How to report results
 

What is tympanometry?

Tympanometry is a test where both negative and positive pressure is applied to the middle ear alongside a constant probe tone. Tympanometry assesses how much of the probe tone is absorbed into the middle and inner ear, and how much is reflected. This allows clinicians to form a picture of how the tympanic membrane acts and functions. 

 

What is a tympanogram?

A tympanogram is a graph produced by tympanometry. It shows the movement of the tympanic membrane and is most often cone-shaped. The peak of a tympanogram is where the eardrum is balanced between negative and positive pressure. By using a template such as Jerger’s classification, it is possible to determine if the tympanic membrane moves freely or if a disorder is present.

 

Tympanometry terminology

There are several terms you need to know when performing tympanometry and interpreting tympanograms:

  • Ear canal volume
  • Tympanometric peak pressure
  • Static compliance
  • Gradient

Let’s dive into each below.

 

Ear canal volume

Fowler & Shanks [1] define ear canal volume as “an estimate of the volume of air medial to the probe, which includes the volume between the probe tip and the tympanic membrane if the tympanic membrane is intact, or the volume of the ear canal and the middle ear space if the tympanic membrane is perforated.”

On average, children from 3-5 years of age have an ear canal volume of 0.4-1.0 cc, while the range is 0.6-1.5 cc for adults.

Ear canal volume can help to suggest what middle ear pathology is present.

For example, an ear canal volume >2.0 with a type B tympanogram in children would suggest a perforated tympanic membrane or a patent grommet.

Alternatively, a very small ear canal volume with a type B tympanogram would suggest wax interference.

 

Tympanometric peak pressure

Tympanometric peak pressure, also known as middle ear pressure, is the ear canal pressure at which the peak of the tympanogram occurs [2].

 

Static compliance

Onusko [3] defines static compliance as “the greatest amount of acoustic energy absorbed by the middle ear system (the vertical peak of the tympanic tracing).”

 

Gradient

Fowler & Shanks [1] define the gradient as “an objective measure that describes the steepness of the slope of the tympanogram near the peak.”

 

Tympanogram types

There are several tympanogram types, as proposed by Jerger:

  • Type A
  • Type B
  • Type C
  • Type As
  • Type Ad
  • Tympanic membrane perforation

Before covering each below, please note that the classification of tympanogram types differs between clinics and audiologists.

The below merely provides an overview of which tympanograms you may come across and what they may indicate.

 

Type A tympanogram

Figure 1 shows what a type A tympanogram looks like:

Type A tympanogram

Figure 1: Type A tympanogram.

Type A tympanograms exhibit the following characteristics:

  • Sharp peak
  • Middle ear pressure between -99 to +50 mmH2O
  • Static compliance between 0.3-1.6 cc in adults
  • Static compliance between 0.2-0.9 cc in children 3-5 years of age
  • Ear canal volume within normal range

 

Type B tympanogram

Figure 2 shows what a type B tympanogram looks like:

Type B tympanogram

Figure 2: Type B tympanogram.

Type B tympanograms exhibit the following characteristics:

  • No peak
  • Non-measurable or reduced middle ear pressure
  • Non-measurable or reduced static compliance
  • Ear canal volume within normal range

 

Type C tympanogram

Figure 3 shows what a type C tympanogram looks like:

Type C tympanogram

Figure 3: Type C tympanogram.

Type C tympanograms exhibit the following characteristics:

  • Sharp peak
  • Middle ear pressure below -99 mmH2O
  • Static compliance between 0.3-1.6 cc in adults
  • Static compliance between 0.2-0.9 cc in children 3-5 years of age
  • Ear canal volume within normal range

 

Type As tympanogram

Figure 4 shows what a type As tympanogram looks like:

Type As tympanogram

Figure 4: Type As tympanogram.

Type As tympanograms exhibit the following characteristics:

  • Sharp peak
  • Normal middle ear pressure
  • Static compliance below 0.3 cc in adults
  • Ear canal volume within normal range

 

Type Ad tympanogram

Figure 5 shows what a type Ad tympanogram looks like:

Type Ad tympanogram

Figure 5: Type Ad tympanogram.

Type Ad tympanograms exhibit the following characteristics:

  • Sharp peak
  • Normal middle ear pressure
  • Static compliance above 1.6 cc in adults
  • Ear canal volume within normal range

 

Tympanic membrane perforation

Figure 6 shows what a tympanogram would look like if the patient’s tympanic membrane is perforated:

Tympanic membrane perforation tympanogram

Figure 6: Tympanic membrane perforation tympanogram.

  • No peak
  • Non-measurable or reduced middle ear pressure
  • Non-measurable or reduced static compliance
  • Large ear canal volume
 

Reasons for repeating tympanometry

If you patient swallows, talks, laughs, coughs or similar during the test, then you may want to repeat the test for more reliable results.

If you get an odd result that does not look correct or does not match the audiogram findings, then you may want to repeat the test to see if the results are repeatable.

 

How to report on tympanometry results

You can find some common sentences used to report on tympanometry results below.

Please note that you should look at tympanometry results in conjunction with other audiological results in the test battery, such as tone audiometry or speech audiometry.

 

Type A

Tympanometry showed normal middle ear pressure and static compliance.

Type B

Tympanometry showed no measurable middle ear pressure or static compliance, consistent with middle ear pathology.

Type C

Tympanometry showed significant negative middle ear pressure in the presence of normal static compliance, consistent with Eustachian tube dysfunction or middle ear pathology.

Type As

Tympanometry showed normal middle ear pressure with decreased static compliance, consistent with a hypomobile tympanic membrane.

Type Ad

Tympanometry showed normal middle ear pressure with increased static compliance, consistent with a hypermobile tympanic membrane.

Large ear canal volume

Tympanometry showed a large ear canal volume, consistent with a tympanic membrane perforation or patent grommet.

 

References

[1] Fowler, C. G., & Shanks, J. E. (2002). Tympanometry. In J. Katz (Ed.), Handbook of clinical audiology (5th ed.). (pp. 175 – 204). Baltimore: Lippincott Williams & Wilkins.

[2] Margolis, R. H., & Hunter, L. L. (2000). Acoustic Immittance Measurements. In  R. J. Roeser, M. Valente & H. Hosford-Dunn (Ed.), Audiology diagnosis. (pp. 381 - 423). New York: Thieme Medical Publishers, Inc.

[3] Onusko, E. (2004). Tympanometry. American Family Physician, 70 (9), 1713 – 1720.

November 2013

Introduction
This Quick Guide is intended to provide information at a beginner level to assist the reader in their understanding of Real Ear Measures (REM). It will also explain some of the common terminology used for REM and within the Affinity 2.0 and Callisto™ software.

Why perform Real Ear Measures?
Not all hearing losses can be resolved by the same method, there are often many differences in the type of
Hearing Devices they are prescribed, the patient’s unique ear canal acoustics and the method in which the
Hearing Device is passing sound into the ear. Real Ear Measures help to overcome these differences by allowing the Audiologist to objectively measure and verify the sound that is being delivered at the ear drum.

The benefits of this process can be applied in varying scenarios from initial hearing aid fitting to troubleshooting. As a consequence, performing this method can help to gain better satisfaction from your patient from their first fitting and less follow up appointments.

REM can only be performed for Hearing Devices which deliver sound via an Air-Conduction method and not for devices which deliver sound via Bone-Conduction or Electrophysiological stimulation.

REM can be performed via three methods, Real Ear Insertion Gain, Real Ear Aided Gain and Real Ear Aided Response. All three achieve the same objective in fitting the hearing aid for the patient and they are all equally as efficient as one another. It is just a preference of which method is used.

What is the basic process of REM?
REM mainly involves placing a fine probe microphone into the ear canal to measure the sound at the ear drum. These measures include the response of the ear canal acoustics and the hearing aid and can help the clinician to adjust the hearing device specifically to the patients’ ears.

The REM process usually involves the following steps once hearing assessment has been performed. 

  1. Calibration of the Probe Microphone – this step can be performed without the patient being present and involves aligning the external microphone with the probe microphone to compensate for any differences between the two. A stimulus is then played and a trace will appear onscreen similar to below.


    This process sets up the conditions to allow comparison between the external microphone and the internal probe microphone. Once placed in the ear canal this will show the effect of the ear canal and hearing device amplification.

    The calibration can be checked in the upcoming REUG measure through running a measurement in the same configuration as the calibration. When this is done a flat trace with a gain value at 0dB should be shown, please see the example below.

  2. Real Ear Un-Aided Gain (REUG) – this step is the first to be performed when the probe microphone has been positioned in the ear. It is purely a measurement of the ear canal without any Hearing Device applied and shows the patients ear acoustics. This will display a trace similar to the below, peaking between 2-4kHz and intersecting the x-axis at 6kHz between 0 and -5dB.


    Performing this measurement allows you to make a consideration of the ears natural amplification of sound; this ensures that you are not fitting your hearing aid to over-amplify in certain regions of the frequency response.

  3. Real Ear Occluded Gain (REOG) – this measurement involves the placement of the hearing device on the ear but muted/off. It allows consideration of the attenuation caused by the ear-piece and its obstructing effect of external sounds. This trace is usually performed with the REUG in view so that they can be compared – the difference between these curves is the amount of attenuation that the ear- piece is providing.


  4. Real Ear Aided Response (REAR) or Real Ear Aided Gain (REAG) – this is a measure which involves the enabled/on hearing device being positioned on the ear with the ear-piece inserted as per normal use and the probe microphone inserted. This allows measurement of the hearing device’s amplification effect within the patients’ ear and includes the effect of the patients ear acoustics. This measure can be run at varying intensities but it is recommended that it is run at speech level (65dB) to ensure that the device is analyzed for the intensity that it will normally be used for.

    It is often during this measurement that adjustment to the Hearing Device Manufacturers software is performed to help match a prescription target. 

  5. Real Ear Insertion Gain (REIG) – this is a measure which is performed in the exact same configuration as the REAR and REAG above but requires the REUG to be performed in advance of it. It does this because it only displays the dB gain view of what the hearing aid is doing and removing the REUR acoustics from this display. Please see the example of this below.

    Again, it is common to make adjustments in your Hearing Device Manufacturers software to alter the response towards the prescription target following this measure.
    It is essential to perform REAR, REAG and REIG at normal speech level (65dB) and some prefer to measure and adjust for soft (50dB) and loud (80dB) intensities also.

When do I use Calibrate for Open Fit?
When performing REM the stimulus needs to be maintained at the point of the patients head to ensure an accurate measurement is made.

This can be difficult when making REM measurements with Open Fit Hearing Aids because there is a lot of sound which leaks out of the ear canal and on to the reference microphone. Therefore the method used to perform REMs needs to be changed.

The two methods used are as follows:

  1. Active Reference Method – this involves the external reference microphone on the REM headset monitoring and altering the stimulus from the speaker during the measurement. This is the best method to apply when measuring with occluding ear-pieces as there is minimal sound leakage onto the reference microphone.

    The Affinity2 and CallistoTM is performing REM by default under this method.

  2. Substitution or Stored Equalization Method – this involves a quick measurement prior to performing your Real Ear Measures to store the distance of the headset from the speaker. This ensures that constant signal intensity is maintained to achieve the measurement level at the patients head. However, this requires your patient to be very still to ensure an accurate measurement.

    This method of performing REM is activated following ‘Calibrate for Open Fit’. This can be added as part of your REM test battery.

December 2013

What is ASSR?
An auditory steady-state response (ASSR) is an electrophysiological response that is evoked by a periodically repeated (rapid) auditory stimulus. An ASSR typically uses frequency specific stimuli (0.5, 1, 2, 4 kHz) with the goal of creating an estimated audiogram. In other words, it is a test used for performing a threshold assessment.

Unlike auditory brainstem response (ABR) which looks at amplitude and latency of the response in the time domain, ASSR looks at amplitudes and phases in the frequency domain. Responses are detected using a statistic-based mathematical detection algorithm to determine if a response is present or not. Another difference is that while it is only possible to test one frequency per ear at a time in frequency-specific threshold ABR. ASSR allows for binaural testing; four frequencies in each ear at the same time (eight simultaneous presentations).

To convert the ASSR responses detected in nHL to eHL (estimated Hearing Levels), a correction factor is typically applied to each response to arrive at the final audiogram. Note that the estimated threshold cannot exceed 0dB eHL.

Figure 1: Estimated Audiogram in ASSR module

Why do ASSR?
The ASSR technology is completely objective and based on statistical probability rather than subjective assessment of response waveforms. The most important audiological application of ASSR is to provide an estimate of the pure tone audiogram, which is used for rehabilitation purposes.

How to test?
Patient Preparation is very important. The electrode sites must be prepared and cleaned in order to obtain acceptably low skin impedance. It is recommended to have impedance values below 3kΩ or lower.

The same electrode placement for ABR is used for ASSR testing allowing for easy switching between the test types.

Electrode Placement (example)
Make sure that the patient is relaxed prior to starting the test. You can monitor this by watching the EEG. Window in the top right hand corner of the recording window. A relaxed patient will typically show black EEG curves within a ±40 volt rejection setting.

Setting up the Eclipse
The Eclipse ASSR software comes with pre-programmed protocols, so the system is ready to use immediately. Protocols can be created or modified easily to fit your clinic need. Consult your manual to learn how to create or modify a protocol. The procedure described below is simply a suggested test process and to be used only as a guideline.

Basic ASSR Test Procedure
Starting ASSR from OtoAccess™ or NOAH

  1. Switch on your PC and wait for Windows® to start.
  2. Double click on the OtoAccessTM or NOAH icon 
  3. Choose an existing client or enter and save a new client.
  4. Double click on the ASSR icon 

Performing an ASSR measurement

  1. Select desired ASSR test protocol.
  2. Adjust the rejection level if rejection occur and if possible instruct patient to relax.
  3. Click on the Start button to begin the ASSR test.
  4. As results are obtained, additional test intensities can be selected by right clicking within the desired frequency panel. From here it is also possible to extend or stop the test.
  5. Click on the Audiogram tab, to see the Estimated Audiogram anytime.
  6. Correction is typically applied using a correction table or by manually dragging audiogram points using the mouse.
  7. Click on the print button in the toolbar or choose Print under the File menu.
  8. Click on the Report button. Select a report template. Modify text if needed. 
  9. Click on the save and exit button in the toolbar.

Other Helpful tools

Temporary change to Auto Test
Prior to starting a test, the default selection of frequencies to be tested can be modified in the “Stimulus” section in the upper left hand corner of the recording screen. 

Temporary Setup
Disable or enable frequencies, change intensities, adjust parameters for patient arousal state etc., temporarily for this session. (See the manual for more information. Changes are effective in the current session only and will NOT permanently change the test protocol. Masking is also applied from the Temporary setup if required.

Browse between historical sessions
Use the PgUp and PgDn keys to toggle between historical sessions. Or select them manually from the Menu bar.

Toggle between 40Hz & 90Hz stimulation rate
Two different stimulus rates are available: 40Hz and 90Hz. 90Hz is typically used for infants and sleeping adults while 40Hz is gaining popularity for its typically strong response in awake adults.

ASSR Shortcuts
Ctrl + S Save session
Ctrl + P Print session
Ctrl + F7 Temporary setup F2 Run test
F4 Pause / resume test F7 Report
Alt + X Save and exit

March 2015

In the field of audiology, we are often presented with different quantities expressed in units of 'decibel'.

This brief guide offers you an overview on the most important details to know about the decibel.

 

What is a decibel?

The decibel (dB) takes its name from Alexander Graham Bell, the inventor of the telephone. The dB (a 10th of a Bel) was derived from the attenuation of a signal transmitted along a mile of telephone cable. The dB was linked with audiology from the beginning because this mile of attenuation was considered the smallest amount of signal change that the average listener could detect.

 

The decibel suffixes

In audiology, many different suffixes are appended to the unit of the dB. The most used are dB SPL and dB HL (Figure 1).

A bird’s peep described as dB SPL, which is the local pressure deviation caused by a sound wave. A woman hears the bird’s peep in dB HL, which is how loud she hears the tone.

Figure 1: Difference between dB SPL and dB HL.

 

Sound Pressure Level (SPL)

dB SPL is the measured pressure relative to 20 micropascals.

This 20-micropascal reference was selected because it was the quietest sound pressure level that a group of normal hearing test subjects could detect.

dB SPL is an absolute and frequency-independent unit.

It is the unit most often used in the calibration of signals in hearing testing equipment.

All other suffixes used in acoustics to describe loudness are calculated from the SPL value.

 

Hearing Level (HL)

dB HL refers to the hearing ability of a person and gives a statement about the severity of the hearing loss.

Hearing levels are measured with pure tones at different frequencies and the hearing level of an individual will vary depending on the frequency chosen.

Normal hearing is defined as 0 dB HL.

If a person has a hearing loss of 60 dB HL at 1 kHz, then he or she cannot hear a pure tone that is presented below 60 dB HL.

 

Normalized HL (nHL)

The notation of nHL is a reference to the frequency-specific threshold of normal hearing subjects.

It describes the intensity level of stimuli used in the field of electrophysiology (ABR, ASSR, and so forth).

We use a correction factor added on top of the SPL value to calculate the nHL value.

March 2016

Using the Print Wizard
In the Print Wizard you have the option to create customized print templates which can be linked to individual protocols for quick printing. The Print Wizard can be reached in two ways.

  1. If you want to use a template for general use, or select an existing one for printing: Go to Menu/ File/Print Layout... in any of the Affinity 2.0 Suite tabs (AUD, REM or HIT)
  2. If you want to create a template or select an existing one to link to a specific protocol: Select the Module tab (AUD, REM, or HIT) relating to the specific protocol and select Menu/Setup/AC440 setup, Menu/Setup/REM440 setup, or Menu/Setup HIT440 setup. Select the specific protocol from the drop down menu and select Print Setup at the bottom of the window.

    There is an additional quick guide to explain how to create a template, it is titled ‘Quick Guide – Customised Printout Setup’.

Now the Print Wizard window opens and shows the following information and functionalities:

    1. Underneath Categories you can select
      • Templates to show all available templates
      • Factory defaults to show only standard templates
      • User defined to show only custom templates
      • Hidden to show hidden templates
      • My favorites to show only templates marked as a favorite
    2. Available templates from the selected category are shown in the Templates viewing area.
    3. Factory default templates are recognized by the lock icon. They ensure that you always have a standard template and do not need to create a customized one. However, in order to edit these default templates, they need to be saved under a new name. User defined/created templates can be set to Read-only (showing the lock icon), by right clicking on the template and selecting Read-only from the drop down list. Read-only status can also be removed from User defined templates by following the same steps.
    4. Templates added to My favorites are marked with a star. Adding templates to My favorites allows quick viewing of your most commonly used templates.
    5. The template that is attached to the selected protocol when entering the print wizard via the AC440 or REM440 window is recognized by a checkmark.
    6. Press the New Template button to open a new empty template.
    7. Select one of the existing templates and press the Edit Template button to modify the selected layout.
    8. Select one of the existing templates and press the Delete Template button to delete the selected template. You will be prompted to confirm that you want to delete the template.
    9. Select one of the existing templates and press the Hide Template button to hide the selected template.
      The template will now be visible only when Hidden is selected under Categories. To unhide the template, select Hidden under Categories, right click on the desired template and select View/Show.
    10. Select one of the existing templates and press the My Favorites button to mark the template as a favorite. The template can now be quickly found when My Favorites is selected under Categories. To remove a template marked with a star from My Favorites, Right-click on the template and press the My Favorites button.
    11. Select one of the templates and press the Preview button to print preview the template on screen.
    12. Depending how you reached the Print Wizard, you will have the option to press
      1. Print for using the selected template for printing or press
      2. Select for dedicating the selected template to the protocol from which you got into the Print Wizard.
    13. To leave the Print Wizard without selecting or changing a template press Cancel.

Right clicking on a specific template provides a drop down menu offering an alternative method for performing the options as described above:

Further information on this can be found in the Callisto and Affinity Additional Information Guides.

December 2013

Introduction
This Quick Guide is intended to give a brief introduction on how to create and configure custom print layouts in the Affinity 2.0 and Callisto™ software suites.

The Affinity 2.0 and Callisto™ software suites have the ability to allow custom print layouts to be created and used alongside the VIOT Suite and Titan Suite. This enables data from various tests to be combined into one convenient printout.

Creating a Custom Print Template
Opening the Print Wizard:

  1. Open the Affinity 2.0 or Callisto™ Suite from your patient management system, Noah, OtoAccess™, or stand- alone.

  2. You can access the setup for protocols from any of the AUD, REM or HIT (Affinity 2.0 only) tabs.

  3. Press, Menu, Setup and then AC440 Setup (or REM440/HIT440 depending on which module you are in). Performing this action will open a new window.

  4. In the new window you will find Print Setup in the bottom left corner. Please press this to open the Print Wizard.

Designing a New Customised Print Template

  1. Now that you are in the Print Wizard you will see the below screen:

    This screen is further clarified by the quick guide titled; ‘Quick Guide – Print Report’.
  2. Click on the blank page in the top right of the screen to create a new print layout. This action will open a new screen. You can alternatively right click on an existing print layout and select Edit to continue building it.

  3. Once in this new screen you will see the elements which you can add to the layout on the left of the screen. These are ordered by their corresponding test module, for example everything to input into the print template to do with the AUD module can be found under AUD.

    All of these elements are able to populate on printing should the patient have these test types assigned to their profile in your patient management system, Noah or OtoAccess™.

  4. Please select an object from the left to draw onto your page. In this example I am using an Audiogram. Once Audiogram has been clicked you will need to draw it to your desired size onto the page.

  5. Once drawn you will be able to move it to your desired position and also right click to define the parameters of what information it displays. For example, in this instance right clicking on the object will allow you to ‘select type’, clicking on this will open a new window which will allow you to define options such as the test ear and include sound examples etc. Every object you input allows for customization of the options the element can display, and the options available to each can vary depending on the module element selected.

    Also, when right clicking on an element you have the options to rotate that element and also toggle the surrounding border.

  6. Once you have clicked in all of your elements and have configured them to your preference you will need to organise them. This can be done by moving them to their desired position and sizing them similarly also. There are a few tools to assist you with this. If you left click on an element you will notice the highlighted tool bar below become active. The options available to you’re here are purely for ordering (ex: to send items backward/forward).

  7. However, if you left-click on one element and then hold Control on your keyboard and left clik on another you will then be able to activate the rest of this tool bar. This opens up the sizing and alignment options to you. Hovering your cursor over each icon in this toolbar will explain its function.

    These settings make it easier to match the sizes of the elements you have added to your print template.

    I have performed the ‘make equal size’ option below as an example.





    Notice how the first element clicked is taking settings (size) from the second element.

  8. Continue to click and add further aspects of your print template to your preference. Once completed you can add information on your clinic (via a blank Test box) and even a logo. This can be done via the General sub-tab on the left of the screen.

    Drawing a logo element will allow you to create a section on your print template for which you can import a .jpg file. To do this, right click on the element and click Select image... This will open the system dialogue where you can navigate to the image that you wish to input. Please note that the Print Wizard only accepts .jpg and .png format image files.


  9. Finally I will add a text box below the logo to show the sites address and contact details.




    You can also alter the font and formatting of the text and how it will appear on your print layout in this section. This text box will be common to this print layout when it is printed from in the future.

Saving your print template

  1. Now that you have completed your print template and have designed it to your preference and requirements you can click on Save or Save As... in the top left of the screen.
  2. As this is a new print layout Save will perform the same action as Save As... and a small window will appear requesting you to title your print layout.

    Once you have titled this layout and Ok is clicked it will appear in your Print Wizard as a new layout.

    Please see the Quick Guide titled ‘Quick Guide – Print Report’ on how to set this as a default or a favorite. Should you require additional information on this then please see the Affinity 2.0 and Callisto™ Additional information guides.

December 2013
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