speech masking

[Dustbug10]

I wanted to get some input on everyone's views. When determining the need to mask for speech, I have been instructed by multiple preceptors to compare the presentation level in the test ear to the bone conduction threshold in the non-test ear at 2kHz. Obviously if the difference exceeds the interaural attenuation level of the transducer you are using, contralateral masking would be necessary. However, I have read in text that because speech noise is a broadband stimulus, you should account for multiple frequencies in the nontest ear(with the exception of 250Hz). Thus you would compare the PL with the best BC threshold at any frequency in the NTE.. Any thoughts or experiences?

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[audprofess]

You are correct that, because speech is a broadband stimulus, you should account for multiple frequencies in the NTE. The problem with the 2 kHz rule is that, if someone has better BC thresholds at other speech frequencies in the NTE, they could possibly be using those other frequencies to detect or understand the speech. The most conservative rule is, as you mentioned, to compare the PL test ear with the best BC threshold in the NTE. An alternate rule that is slightly less conservative, but still usually safe, is to compare the PL test ear with the 2-frequency BC PTA of the NTE.

 

[AUDball2012]

You are correct that, because speech is a broadband stimulus, you should account for multiple frequencies in the NTE. The problem with the 2 kHz rule is that, if someone has better BC thresholds at other speech frequencies in the NTE, they could possibly be using those other frequencies to detect or understand the speech. The most conservative rule is, as you mentioned, to compare the PL test ear with the best BC threshold in the NTE. An alternate rule that is slightly less conservative, but still usually safe, is to compare the PL test ear with the 2-frequency BC PTA of the NTE.

I agree. I actually have never heard of the 2kHz rule. I have always heard to use the best bone.

The problem I have is an efficiency issue. When I test word rec, I always do it before bone...therefore you cant use the best bone rule. In order to do it after bone, you would have to go in, switch out the ear phone, put on the BC vibrator, then go back in to switch out the BC vibrator with the inserts---not efficient. So I always mask for word rec by going 20 dB below my PL in the contra ear.

 

[cidanu]

So I always mask for word rec by going 20 dB below my PL in the contra ear.

ditto. never heard of the 2K rule but have used the difference btw the test ear and BC. I suppose it could help in cases of overmasking.

 

[AuD123]

Speech masking should be done for SRT and WR according to the following rule: If the presentation level threshold minus the IA is greater than the best BC threshold of the NTE, then you ought to mask (speech being a broadband stimulus and good thresholds at lower frequencies will allow for surprising audibility). When looking at the 2 kHz rule you described, the trick is to think about all of those patients with steeply sloping audiograms, but hearing sensitivity WNL at 250 and 500 - amazing how much they can hear, right? This gives a clear indication of the need to mask when thesholds for BC in the NTE at low frequencies are decent or even WNL. In terms of how much to mask, there are a variety of formulas available. The easiest rule is to just put 20 dB less than the presentation level into the NTE (e.g. Test ear 60 dBHL, NTE 40 dBHL Speech noise), though this can be a problem if there are conductive problems in the NTE.