Threshold Equalizing Noise (TEN) Test

What is the threshold equalizing noise (TEN) test?

The threshold equalizing noise (TEN) test measures pure tone thresholds with a special masking noise called TEN. The TEN test is a quick and easy way to identify cochlear dead regions.

What is a cochlear 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 neighbouring hair cells, if the intensity of the signal is loud enough. This is because the pure tone produces sufficient basilar-membrane vibrations in neighbouring areas of the cochlea, where there are surviving IHCs and neurons. This phenomenon is defined as “Off Frequency Listening”. Clinically, this will be presented 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 (Moore, 2009):

• Severe to profound hearing loss
• Absolute threshold at a specific (suspected) frequency is 70dB HL or greater
• Steeply sloping hearing loss
• Complaints of distortion
• Extremely poor speech discrimination

TEN test procedure

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.  

1. On the device press and hold the Tests button and use the black scroll wheel to select TEN: Threshold-equalizing noise. The test is set to start with the stimulus for channel 1 and 2 directed to the same ear. The tone is presented in channel 1 and TEN is presented in channel 2, with the stimulus in channel 2 reversed (Rev) to have a continuous masking signal.

If operating the audiometer from the PC the TEN noise will be available in channel 2 if licensed. To enable the TEN noise press TEN (a).  Ensure it is presented to the same ear as in channel 1 (b). The decibel step size can be changed to 2dB (c).

2. Set the intensity levels:
   • For frequencies where hearing loss up to 60dB HL: set the TEN level to 70dB
   • For frequencies where hearing loss is 70dB or more: set the TEN level 10dB above the audiometric threshold at that frequency (Moore, 2009). E.g., if the audiometric threshold is 75dB HL, set the TEN level to 85dB HL
   • If the TEN is too loud, or if the maximum TEN level of 90dB HL is reached, then set the TEN level equal to the audiometric threshold. This should still give a definitive result

3. Conduct a threshold search using the traditional method for air conduction 4. Repeat for each frequency where a dead region is suspected

Criteria for diagnosing a cochlear dead region (Moore, 2009)

A dead region at a particular frequency is indicated when a masked threshold is at least 10dB or more above the level of the TEN and the masked threshold is at least 10dB above the non-masked threshold.

The example below shows an example of a positive TEN test, with a masked threshold indicating a dead region. 

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).

Benefits of identifying a cochlear dead region

• Help counsel the patient and manage expectations regarding the potential benefit of hearing aids.
• Helps on choice of type of hearing aid.
• Can help determine if a patient would be a good candidate for cochlear implants o Patient might do better with an implant when there are extensive dead regions o Helps determine insertion depth.

References

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”.