Hearing aids and cochlear implants improve hearing for people with different degrees of hearing loss, but there are some situations in which listeners using these devices are at a significant disadvantage compared to people with normal hearing.
These situations include listening to speech in noise, music, environmental sounds, and to sounds that are either too loud or too soft. In particular, most cochlear implant recipients have difficulty appreciating aspects of music, including the perception of pitch and music produced by multiple instruments.
The Institute has completed several research projects with the common aim of improving sound perception for people with cochlear implants and/or hearing aids. These included basic psychophysical studies to understand the neural and psychological mechanisms of sound perception, development of new sound-processing strategies, and training studies.
Improving auditory stream segregation
Music perception and intelligibility of speech in a noisy environment are related to the ability to segregate different sounds according to their source. People with impaired hearing have reduced abilities for auditory stream segregation compared to people with normal hearing.
We studied the cues used by people with normal and impaired hearing in order to provide cochlear implant and hearing-aid users with enhanced signals which will improve their ability to separate sounds that occur simultaneously but come from different sources. This enabled better perception of speech in noise and music.
Improving music sound quality with cochlear implants
Different instruments have very different sounds. For instance, a trumpet and a violin playing the same note are easily distinguished by people with normal hearing. However, cochlear implant users can find it difficult to distinguish between different instruments, or between sounds that are harsh or smooth.
The ability to distinguish between similar sounds from their timbre is important to recognise a speaker’s voice or a musical instrument. Timbre also conveys emotional information through the harmony and the roughness of the sounds. It is therefore crucial in order to appreciate music fully.
We tested how well cochlear implant users can tease apart melodies played with different types of sounds. This information will be used to develop and test new sound-processing algorithms and training techniques to help cochlear implant users enjoy music more.
Innovative sound processing strategies
Real-time implementations and evaluations of bimodal, STAR, and travelling wave strategies are in progress. Bimodal refers to people using electrical stimulation from a cochlear implant in one ear together with acoustic stimulation from a hearing aid in the other ear.
Spike-based temporal auditory representation (STAR) is a sound processing strategy based on the way sound is processed in the human auditory system. Travelling-wave strategies include relative timing information for different sounds as they travel from one end of the cochlea to the other.
Musical training in children with hearing loss
Soon after receiving a cochlear implant, young children have extensive training in speech recognition and language skills. However, musical training is usually left to the parents, and to the child’s desire to learn. Often a lack of immediate results compared to their friends with normal hearing reduces their motivation to play music. However, if the children and the teacher can anticipate their rate of learning they may be able to adjust their expectations and maintain motivation. To test this hypothesis, a project was conducted with teacher Christine Storey and a group of children attending Yarra Valley Grammar School.
Multipolar focused electrical stimulation
Bimodal perception of music
Spiking neural network model of auditory learning
Interior Design: Music for the cochlear implant
Speak Percussion performing at Interior Design