CDs for Diagnosis of Dead Regions in the Cochlea –  TEN(HL)  and TEN(ER3)

 1. Background

Dead regions are regions in the cochlea where there are no functioning inner hair cells and/or neurones.  A dead region is defined in terms of the range of characteristic frequencies in the cochlea that would normally be associated with that region.  When a person has a dead region, there may be little or no benefit in applying amplification (via a hearing aid) for frequencies well inside the dead region.  Indeed, such amplification may impair speech intelligibility.  However, for people with high-frequency dead regions, there may be some benefit in applying amplification for frequencies up to about 70% higher than the “edge frequency” of the dead region (Vickers et al., 2001; Baer et al., 2002). 

The TEN(HL) CD and the TEN(ER3) CD contain stimuli for implementing a simple test for detecting the presence of dead regions and defining their limits.  The test is a simplified and improved version of the test described in Moore et al. (2000).  The TEN(HL) test is described in Moore et al. (2004).  This version of the test is suitable for use with Telephonics TDH39, TDH49 and TDH50 headphones.  The TEN(ER3) test is described in Moore et al. (2012).  This version of the test is suitable for use with Etymõtic Research ER-3A insert earphones.

It is intended that the signals from the CD are fed through an audiometer.  The methods used to conduct the test are similar to those used for conventional pure-tone audiometry, except that the signal threshold is measured in the presence of a continuous background noise and a 2-dB final step size is used to measure thresholds. 

The test involves measuring the threshold for detecting a sinusoidal tone presented in a special background noise called “threshold-equalising noise”.  Hence the test is referred to as the "TEN" test.  In the first version of the test, the noise was spectrally shaped so that the masked threshold, specified in dB SPL, was approximately the same for all frequencies in the range 0.25 to 10 kHz, for people with normal hearing and people with hearing impairment but without any dead regions.  For the TEN(HL) and TEN(ER3) tests, the noise is designed to give equal masked thresholds in dB HL, over the more limited frequency range 500 to 4000 Hz.

The expected masked threshold, when a dead region is not present, is approximately equal to the nominal level of the noise specified in dB/ERBN, where ERBN stands for the equivalent rectangular bandwidth of the auditory filter, measured using normally hearing people at moderate sound levels (Glasberg and Moore, 1990; Moore, 2012).  For example, a level per ERBN of 60 dB leads to a masked threshold of about 60 dB HL.  As all calibrations are in HL, absolute thresholds (audiometric thresholds) can be measured either using the tones generated by the audiometer, or using the test tones from the CD; the results should be very similar.  Also, unlike the first CD, the nominal level of the noise and the level of the test tone at each frequency both correspond to the level indicated on the audiometer.  For example, a dial reading of 60 dB will lead to a noise level of 60 dB HL/ERBN for the TEN and a level of 60 dB HL for the tone.  

Dead regions for a particular frequency are indicated by a masked threshold that is at least 10 dB above the absolute threshold and 10 dB above the nominal noise level per ERBN.  If there is any ambiguity, for example, if the masked threshold is higher than normal, but is only 5 dB above the absolute threshold, then, when possible, the test should be repeated with a higher noise level.

Full instructions for applying the test are contained in the leaflet that comes with the CDs.

References

Baer, T., Moore, B. C. J., and Kluk, K. (2002). "Effects of lowpass filtering on the intelligibility of speech in noise for people with and without dead regions at high frequencies," J. Acoust. Soc. Am. 112, 1133-1144.

Glasberg, B. R., and Moore, B. C. J. (1990). "Derivation of auditory filter shapes from notched-noise data," Hear. Res. 47, 103-138.

Moore, B. C. J. (2012). An Introduction to the Psychology of Hearing, 6th Ed. (Emerald, Bingley, UK).

Moore, B. C. J., Glasberg, B. R., and Stone, M. A. (2004). "New version of the TEN test with calibrations in dB HL," Ear Hear. 25, 478-487.

Moore, B. C. J., Huss, M., Vickers, D. A., Glasberg, B. R., and Alcántara, J. I. (2000). "A test for the diagnosis of dead regions in the cochlea," Br. J. Audiol. 34, 205-224.

Moore, B. C. J., Creeke, S., Glasberg, B. R., Stone, M. A., and Sek, A. (2012). "A version of the TEN test for use with ER-3A insert earphones," Ear Hear. (submitted).

Vickers, D. A., Moore, B. C. J., and Baer, T. (2001). "Effects of lowpass filtering on the intelligibility of speech in quiet for people with and without dead regions at high frequencies," J. Acoust. Soc. Am. 110, 1164-1175.

 

2.  Obtaining the TEN(HL) CD  or the ER-3A CD

The preferred method of payment is by cheque or money order in pounds sterling or US dollars. 

For the TEN(HL) CD, the cost is UK £15 or US $32, including shipping.
For the ER-3A CD, the cost is UK £20 or US $40, including shipping.  
The cheque/money order should be made payable to B.C.J. Moore and sent to:

Prof. Brian C.J. Moore,

Department of Psychology,

University of Cambridge,

Downing Street,

Cambridge CB2 3EB,

England

Be sure to include the mailing address where the CD should be sent.