Room Setup Position
Why do the children need to be looking straight ahead at the DVD player?
The aim is for the subject to be facing the loudspeaker straight on so that the sound goes equally to both ears; without favouring one ear over the other. In order to keep them facing the speaker, we need to hold their attention in that direction. To do this, we utilise a screen showing something interesting (a movie or children’s show playing from a DVD.) We place the screen and speaker as close as possible together (line of sight wise – the screen can be some distance behind the speaker). The aim is to keep their face pointed towards the speaker. Ideally, we would like the speaker and screen to be exactly in line with each other, as viewed from the subject’s point of view. This is of course impossible, so the next best thing is to have the screen just above the speaker, at the distance between the subject and the speaker, looking up slightly shouldn’t have much effect on the reception of sound in the ears.
If the child’s hearing aids are set to “omnidirectional”, is it okay to have the child facing directly away from the speaker?
i.e. the speaker is directly behind the child’s head ~ 1m away. Both hearing aids are still equally exposed to the test stimulus in this position.
It doesn’t seem a good idea to let the child face away from the loudspeaker as – although the microphones are on ‘omnidirectional’ – the actual hearing aid microphones are more facing forward on the aid shoe, and there likely will be a head shadow effect. This does not mean you shouldn’t try letting the child facing the mother! We’ve done tests before where the child is facing the mother (lying on their shoulder), but the mother now turns 180 degrees (so with her back to the loudspeaker). This is of course not the ideal situation, but sometimes this is the only way to keep the child comfortable. And it seems to work, provided the mother is not blocking the direct path to the loudspeaker. If all else fails, the idea in the question is still a good one, the worst alternative is having to stop the recording, but during evaluation you should take into account (or make a note somewhere) that the testing conditions were not ideal.