What is In-Situ SPL and In-Situ Audiometry?

10 mins
01 August 2017


The term ‘in-situ’ in the context of audiology is often used to refer to when a hearing instrument or other device is being worn.


What is in-situ SPL?

In-situ SPL refers to the characteristics of a sound (sound pressure level at different frequencies), at or near the tympanic membrane when a hearing instrument is in place in (or behind) the ear.


What is in-situ audiometry?

In-situ audiometry determines the hearing thresholds of wearers while they are wearing their devices, using stimuli that are generated by the hearing instrument (rather than the audiometer via headphones or inserts). This technique can bypass the calibration errors that might arise when indirectly calculating the SPL at the tympanic membrane using someone’s thresholds as measured in dB HL (since an average value is often used in this calculation).

Acoustic characteristics of the hearing aid and its coupling (vents, leakage and ear mould characterstics, for example) are also taken into account automatically. Set against these technical advantages, the technique has a potential time penalty in that thresholds might have to be measured twice (e.g. once for diagnosis of hearing loss, with threshold in dB HL via headphones or inserts and once again for verification of the hearing instrument with threshold in SPL via a hearing instrument.)


Michael Maslin
After working for several years as an audiologist in the UK, Michael completed his Ph.D. in 2010 at The University of Manchester. The topic was plasticity of the human binaural auditory system. He then completed a 3-year post-doctoral research program that built directly on the underpinning work carried out during his Ph.D. In 2015, Michael joined the Interacoustics Academy, offering training and education in audiological and vestibular diagnostics worldwide. Michael now works for the University of Canterbury in Christchurch, New Zealand, exploring his research interests which include electrophysiological measurement of the central auditory system, and the development of clinical protocols and clinical techniques applied in areas such as paediatric audiology and vestibular assessment and management.

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