Introduction To

Audiometry

Audiometry is used to measure the sensitivity of hearing across frequencies. During audiometry, sounds are presented to the patient using different types of headphones. This guide will help you to become familiar with the various headphones used, what they test, proper placement, and infection control.

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Types of Headphones

TDH 39

This type of headphone rests on CARL’s ears and is classified as a supra-aural headphone. 

Supra-aural headphones should be wiped clean using the product specified in your infection control guideline and allowed to dry completely or covered in a new set of earphone covers between patients. 

For placement, gently place the headphones on top of CARL’s ears, with the center of the earphone, aimed directly into the ear canal. At the same time, adjust/tighten the headband so that it sits comfortably across the head and stays in the proper position on the ears.

Pros Cons
  • Standard with most audiometers
  • Less expensive than disposable foam tips
  • Easy to use
  • May be uncomfortable
  • Does not block out noise as well as other headphones
  • Poor interaural attenuation
  • May cause collapsed ear canals during testing
  • Less reliable for test-retest of 6-8 kHz

ER3A - INSERT EARPHONES

The foam tip of this earphone is inserted into CARL’s ears and is classified as an insert earphone. 

The foam-tips are single use and should be thrown away after each patient.

For placement, select the largest insert size that will comfortably seal the ear and prevent any sound from escaping. Compress the insert by rolling it in-between your fingers prior to inserting. On an adult, pull the pinna up and back to allow for easier insertion. Ensure the insert is placed at the appropriate depth by inserting until the base (side with the black tubing) of the foam tip is around 2-mm¹ inside the ear canal entrance. Repeat on the other side.

Pros Cons
    • Standard with most audiometers
    • Avoids causing collapsed ear canals
    • Better interaural attenuation
    • Blocks out noise better than TDH
    • Three sizes: small/pediatric, medium/adult, large/jumbo
  • Higher cost to continually replenish

Circumaural Headphones

The Sennheiser HDA 300, Sennheiser 200 HDA, Sennheiser HD280Pro and DD450 are all types of circumaural headphones.

Compare how these fit around CARL’s ears compared to the TDH headphones which rest on top of his ears.  

Circumaural headphones can be used for high frequency threshold testing and with several tablet-based audiometers such as Shoebox and HearX.

These headphones should be wiped clean using the product specified in your infection control guideline and allowed to dry completely or covered in a new set of earphone covers between patients.

For placement, position the headphones around CARL’s ears, with the center of the earphone, aimed directly into the ear canal. At the same time, adjust/tighten the headband so that it sits comfortably across the head and stays in the proper position around the ears.

Pros Cons
  • Blocks out noise well
  • May test high frequencies up to 20 kHz
  • Comes with some portable hearing test systems
  • May be expensive (depending on the type)
  • May be heavy

Bone Conductor

The bone conductor bypasses the outer and middle ear and tests the inner ear for hearing so that the type of hearing loss, found by air conduction, can be determined. Unlike the previous headphones, the bone conductor rests behind CARL’s ear. On a patient, this would sit on the mastoid bone. 

The bone conductor can be wiped clean using the product specified in your infection control guideline. 

For placement, position the bone conductor with the side with the small round protrusion facing inside and sitting flat behind the ear on the bony part of the mastoid. Ensure the bone oscillator is not touching the pinna or resting on any hair.  While holding the oscillator in position, place the other side of the headband comfortably onto the temple area.

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Infection Control

Infection Control guidelines may vary in different areas and local and up-to-date preferred practice guidelines should be taught.

Instructors not familiar with infection control should become familiar with the regulations for their area and could register for overview information presented by audiologyonline on this topic such as:

https://www.audiologyonline.com/audiology-ceus/course/infection-control-current-trends-for-29121

Or review

AU Bankaitis in Handbook of clinical audiology/ editor-in-chief, Jack Katz, editors, Marshall Chasin, Kristina English, Linda J. Hood, Kim L. Tillery. – Seventh edition (2015).  pp: 861-868 Chapter 46 Infection Control

Resources

Headphones (Traditional)

Handbook of clinical audiology/ editor-in-chief, Jack Katz, editors, Marshall Chasin,
Kristina English, Linda J. Hood, Kim L. Tillery. – Seventh edition (2015). Section 1 Basic Tests and Procedures: Equipment Transducers pp: 32-33

Headphones (ALTERNATIVE)

Folkeard, P., Hawkins, M., Scollie, S, Sheikh, B. & Parsa, V. (2019). An evaluation of the
Sennheiser HDA 280-cL circumaural headphone for use in audiometric testing. IJA, 58(7), 427-433. doi.org/10.1080/14992027.2019.1594415


Smull, C.C., Madsen, B. & Magolis, R.H. (2019). Evaluation of two circumaural earphones
for audiometry. Ear and Hearing, 40(1), 177-183. doi.org/10.1097/AUD.0000000000000585ttp://doi.org/10.1097/A


Van der Aerschot, M., Swanepoel, D.W., Mahomed-Asmail, F, Myburgh, H.C. & Eikelboom,
R.H. (2016). Affordable headphones for accessible screening audiometry: an evaluation of the Sennheiser HD202II supra-aural headphone. IJA, 55(11), 616-622. doi.org/10.1080/14992027.2016.1214756

Standards

Handbook of clinical audiology/ editor-in-chief, Jack Katz, editors, Marshall Chasin, Kristina English, Linda J. Hood, Kim L. Tillery. – Seventh edition (2015).  ANSI, IEC and ISO Standards Table 2.1. p.11