Insert Earphones

Insert earphones are foam earplugs with a tube that carries the test signal into the ear. They are intended for use with audiometric equipment and are used to test hearing in audiology clinics, for auditory research, and for screening in industrial and educational settings. Insert earphones are the best choice for hearing tests that need to be conducted in environments where there are high ambient noise levels. The KUDUwave comes with both an ambient dome (headset) and inserts earphones.

In this article, we will unpack answers to the most common questions on KUDUwave insert earphones, but first …

What Is Pure Tone Audiometry?

Pure-tone audiometry is a behavioral test used to measure hearing sensitivity. This measure involves the peripheral and central auditory systems. Pure Tone audiometry, including air- and bone-conduction testing, is conducted to characterize hearing loss by:

  • Type
  • Degree (severity)
  • Sidedness (unilateral or bilateral)

For accurate assessment of hearing in the United States, the American National Standards Institute (ANSI) has established standards for the calibration of clinical audiometers. The output sound pressure level for standard circumaural or inserted earphones, or both, is specified when measured in a standard coupler, referred to as an artificial ear. The artificial ear simulates the impedance characteristics of the average human ear at the plane of the tympanic membrane.

Pure-tone thresholds (PTTs) indicate the softest sound audible to an individual at least 50% of the time.  According to ScienceDirect, clinically pure-tone hearing thresholds at frequencies from 250 to 8000 Hz are determined in the air- and bone-conduction pathways, using headphone/insert earphones and bone conductor respectively.

Q1. Why use insert earphones?

For audiometric results to be valid, the patient must respond to stimulation of the ear being tested. When non-insert earphones are used, sounds greater than 40dB HL presented to one ear can cross over to the opposite ear, most likely with the vibration of the earphone against the skull acting as a bone conductor. The amount of sound needed for crossover to occur is known as the interaural attenuation, which for air conduction is about 50dB HL for lower frequencies and 60dB HL for higher frequencies. The interaural attenuation is considerably higher when insert earphones are used.

A study published in the International Journal of Audiology (2015) investigated the attenuation characteristics and live ambient noise-monitoring feature of the  KUDUwave audiometer. The outcomes showed that the background noise did not affect accuracy using the KUDUwave system, with 92% of thresholds from 250 to 8000 Hz within 5 dB of conventional sound booth audiometry. “Swanepoel et al. (2015) demonstrated a significant improvement of attenuation across frequencies using the combined circumaural earcups and inserts of the KUDUwave headset when evaluated with standard ER-3A insert earphones and TDH-39 supra-aural transducers.”

Q2. What precautions should be taken when inserting the insert earphones?

Insert earphones can become pinched inside the ear canal. This is difficult to see even with a visual inspection because of the circumaural headphones that cover the inserts. If any portion of the sound tube or insert is pinched, it can significantly impact test results. It is, therefore, very important that a trained audiology assistant conduct in-person or tele-audiometry testing.

The insert earphones must be deeply fitted and unpinched by the circumaural headphones in order to properly fit the KUDU equipment and maximize both occlusion effect values and interaural attenuation values.

Q3: Does the depth of insertion affect hearing results?

The depth of the insertion can cause possible threshold differences. Poorer hearing thresholds were noticed when the ear tip was positioned toward the outer part of the ear canal, further away from the eardrum. Low frequencies, as opposed to high frequencies, can be affected by shallow insertions. The optimal insertion is full or intermediate insertion depths for accurate results at any frequency.

Q4. What is the correct way to use insert earphones?

Examine the ear canal for obstruction or excessive cerumen. Visually determine whether you would need to use a different size other than the standard foam ear tip. Make sure the sound delivery tube is not blocked. To facilitate proper placement, firmly roll the foam ear tip into the smallest diameter possible.

Correct insertion depth: When the outside edge of the ear tip is  2-3 mm inside the entrance of the ear canal. Allow foam to expand to acoustically seal the ear canal.

Q5. Can you use inserts again after sterilization?

The KUDUwave inserts are intended to be used only once to ensure hygiene and avoid cross infections. Used inserts need to be discarded and a new insert should be used for each new session.

Q6. Are there any contraindications for inserting earphones?

Any condition that could be exacerbated with the use of insert earphones would be contraindicative to using insert earphones. Using insert earphones when the patient has infection-causing otalgia or ear canal laceration is not advisable.

Q7. Can insert earphones be used in tele-audiometry?

The KUDUwave design uses insert earphones covered by circumaural headphones to achieve ambient noise levels appropriate for diagnostic testing. The inserted earphones must be deeply inserted to attain proper placement in the ear canal, which is crucial for the pre-set interaural attenuation and occlusion effect values programmed into the software. It is, therefore, necessary to conduct tele-audiometry only with the help of a well-trained audiology assistant.