Auditory processing disorder (APD) is a hearing problem caused by the brain not processing sound in the normal way. A person with APD will have normal hearing when tested using standard tests, but will nonetheless have problems making sense of sounds, especially complicated and fast-changing sounds like speech. Children with APD may have noticeable problems from a very young age, such as difficulty understanding speech in the presence of other sounds, for example in a noisy classroom, and expressing themselves with speech. Their reading and spelling abilities may also be affected. There is increasing interest in APD in children world-wide, because of suspicions that it may lead to learning difficulties for language and literacy, and hence to poor school performance. Unfortunately, APD is very poorly understood, with no general consensus of what it really is, or how to diagnose or treat it.
One promising avenue of research concerns spatial listening abilities. Spatial listening involves being able to separate sources of sound from each other based on their location in space. As an example, if a child is sitting in a classroom trying to listen to the teacher who is in front of them while behind them, two other children are having a conversation, they will find it easier to follow the teacher than if the chatting children were very near the teacher. Most people can understand speech much better when interfering noises (or other talkers) are located away from the talker they are trying to listen to, rather than nearby. However, some children suspected of having APD seem to be very poor at doing this.
Although it would be best to measure these spatial listening abilities in real-life situations, it’s often more practical to use headphones and techniques of virtual reality in the lab. Virtual reality can make it seem like sounds are spread out in the world as they are in real life, rather than inside your head, as they typically are when listening through headphones. The drawback to virtual reality is that you need to account for the effects of the listener’s head on sounds – because our heads are all different from one another, what works for one person likely won’t work well for another. Tests of spatial listening in children to date have used standard adult head measurements to create their virtual reality, even though children’s and adults’ heads are very different in size and shape. This mismatch could have an effect on the results being obtained, making them less accurate, and making it harder to interpret the results of listening tests being used to develop diagnostic tests for APD.
The main aim of Katharina’s project is to determine how accurate spatial listening performance as measured by virtual reality is, and how much it depends on taking into account the listener’s actual head size. She will measure spatial listening abilities under three conditions: 1) using virtual reality while taking into account a child’s actual head size, 2) using virtual reality with a default standard head size and 3) in real-life. She will study both children suspected of having APD, as well as normally-hearing children.
A growing number of children are being referred for APD assessment, but few NHS clinics are able to diagnose their problems, not least because there is a great deal of uncertainty about what diagnostic tests to use. A better understanding of the nature of at least some types of APD, as well as more efficient diagnostic procedures, could have an important impact on clinical practice, and improve assessment and rehabilitation of APD.