John Ellwood, Educational Audiologist, Cumbria

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At the BAEA conference mention was made of the CDs produced by the National Acoustics Laboratories in Australia. The three compact disc series contain samples of speech in noise prepared during the 1990's for use in various research studies.

The materials collected on the three CDs include BKB lists, VCV (vowel consonant vowel) lists, SPIN (high predictability vs low predictability) lists, continuous discourse spoken by a variety of talkers and a range of background noises. Its all here so you only have to work out when to and what to use it for.

Although still fairly new to my ever increasing collection of test and evaluation material I have found the first disc very useful. It's the one with 21 BKB word lists presented in equal background noise. As it stands it is very difficult for a normal hearing adult to discriminate a reasonable percentage of the key words.

However, by playing it through the laptop you are able to change the signal to noise ratio. The signal comes through the right speaker and the noise comes through the left, so by changing the balance to decrease the left speaker the background noise can be reduced. By doing this I found that I now had a more flexible speech in noise sentence discrimination assessment. Presentations can be given at +10, +5 and 0 signal to noise ratios (in fact any signal to noise ratio you choose). The sentences can be paced with the pause button and a reasonably scientific evaluation carried out. The down side is the fact that the voices use a 'mild' Australian accent. Still most people understand me, even in Cumbria!

Along with the usual assessment of speech in noise for hearing aid wearers and non hearing aid wearers, I have included the assessment in my battery of tests to determine central auditory processing difficulties and more recently during an acoustic survey of a classroom.

It was found that the signal to noise ratio was constantly around 5dB and to show the effects of this on the children's ability to discriminate speech under these conditions six of the children in the class were asked to do the BKB sentences in noise at the same signal to noise ratio of +5.

The children with normal hearing were selected on their recent English SATs results

Level 32 chd 98%80% discrimination of 50 key words in noise
Level 2B/2A2 chd80%72% discrimination of 50 key words in noise
Level 12 chd 58%76% discrimination of 50 key words in noise

Needless to say the ability to discriminate the BKB sentences showed some correlation with the child's ability measured through their SATs. Within the context of the report this added a little more bite to the effects of poor acoustics on children.

For more information on the CD set email: research@nal.gov.au