New research contributes to assessing whether a room in a hearing clinic is suitable when the hearing aids of tomorrow are to be adapted to infants who are just a few months old.
Room acoustics are an important factor that influences how well hearing aids can be adapted for the smallest children. This has just been shown by a research project, which also points out possibilities for countering the influence of acoustics.
Today, the final assessment of an adaptation of hearing aids is only made when children with hearing disabilities are around nine months old and can complete a test in which they have to react to where a sound is coming from. If the setting has not been optimal, this means that these children have missed significant stimuli from—in particular—speech during the first months of their lives, which it can be difficult to recuperate later on.
“Therefore, we’ve been working for several years to develop a measuring method that makes it possible to assess the adaptations of hearing aids for infants as young as 2-3 months. In this way, we can contribute to providing them with significant input to—in particular—their language and social development,” says Søren Laugesen, Senior Research Engineer in Interacoustics Research Unit. Interacoustics is a Danish company and the world’s largest producer of advanced electronic equipment for diagnosing hearing loss and adaptation of hearing aids.
New measuring methods developed with researchers
The new measuring method is being developed in collaboration with—among other partners—researchers and students at DTU. Here, one step in the process has been to find a solution that involves the acoustics from the room in which the hearing aid is being adjusted.
“The new method for assessing the adaptation of hearing aids in very young infants is based on an Auditory Steady State Response (ASSR) test. In practical terms, this means that we emit a series of audio signals covering several different frequency ranges from a loudspeaker in the room,” says Valentina Zapata-Rodriguez, who has conducted the research project as an industrial PhD student in a collaboration between DTU Electrical Engineering’s Acoustic Technology group and Interacoustics Research Unit.
“The infant is in the same room sleeping, while the electrophysiological measuring is being done. Using electrodes attached to the child’s head, activity in the brain is measured and signals whether the child is registering the sound from the loudspeaker,” explains Valentina Zapata-Rodriguez.
Based on the measurements, it can be determined whether the sound is amplified to the right level or whether there is a need to change the hearing aid settings.
Measurements of acoustics in hearing clinics
Valentina has made measurements of the acoustics in 31 different rooms in hearing clinics in Danish hospitals. The results showed that there are great variations in the acoustics in these rooms that the new measuring method must take into account.
“I’ve subsequently developed models that simulate the acoustics in eight different room types covering the wide range I found in the hearing clinics. I then tested the importance of the acoustics to the ASSR measurement,” says Valentina Zapata-Rodriguez.
The tests were performed in DTU’s advanced sound laboratory AVIL—Audio Visual Immersion Lab—which is equipped with 64 speakers, making it possible to reproduce the acoustics from different room types. A total of 23 test subjects participated in the trial.
Based on these data, it is possible to incorporate information about the acoustics in the future measuring instrument which will be used to assess hearing aids for infants.
"With this new knowledge, it will be possible to measure the acoustics at the outset to establish whether a room in the hearing clinic is suitable for this type of test. It may be better to use a completely different room, or to change the effect from the acoustics by—for example—placing the speaker or the infant elsewhere in the room,” explains Søren Laugesen.
Interacoustics is very pleased with the results of Valentina Zapata-Rodriguez’s work. It has been crucial to the further development of the new test method to acquire knowledge about the influence of the acoustics and the possibility of adjusting the measurements accordingly. The objective is now to be able to introduce the new measuring method on the market within the coming years.