Evaluation of noise reduction in digital hearing aids in situations with multiple signal sources


  • Marlitt Frenz German Institute of Hearing Aids, L¨ubeck, Germany
  • Alfred Mertins Institute for Signal Processing, Universit¨at zu L¨ubeck, L¨ubeck, Germany
  • Hendrik Husstedt German Institute of Hearing Aids, L¨ubeck, Germany


hearing aids, technical measurements, Hagerman & Olofsson, noise reduction, objective measurements


Features of modern hearing aids such as the digital noise reduction and directional microphones can enhance speech. One way to evaluate the effect of these features is to measure the increase of the signal-to-noise ratio (SNR). To this end, the method of Hagerman and Olofsson is often used. However, only two signals can be distinguished with this method, e.g., speech and noise. Since many realistic situations include more than two signals, an extension of the method of Hagerman and Olofsson for an arbitrary number of signals is introduced. To proof the concept, this extended method is applied to a setup with 9 different signals presented by 8 speakers. This study considers a separation of speech and noise for 8 signal sources. All speakers are positioned around a hearing aid on a circle with a radial distance of r = 1m and an angular distance of 45◦ between 0◦ and 360◦. Speech is presented from 0◦ and noise from all 8 directions (0◦,45◦, ...,360◦). With this setup, a stateof- the-art hearing aid is analysed for different settings where the digital noise reduction and/or the directional microphones are turned on or off. As a result, the SNR for all directions can be investigated individually. This demonstrates the practicability of the extended method.


Bentler, R.A. (2005) “Effectiveness of directional microphones and noise reduction schemes in hearing aids: a systematic review of the evidence,” J. Am. Acad. Audiol., 16, 473-484. doi: 10.1177/1084713806289514

Brons, I., Houben, R., and Dreschler, W.A. (2014) “Effects of noise reduction on speech intelligibility, perceived listening effort, and personal preference in hearing-impaired listeners,” Trends Amplif., 18, 2331-2165. doi:

Chung, K. (2004) “Challenges and recent developments in hearing aids: Part I. Speech understanding in noise, microphone technologies and noise reduction algorithms,” Trends Amplif., 8, 83-124. doi: 10.1177/108471380400800302

Hagerman, B., and Olofsson, A. (2004). “A method to measure the effect of noise reduction algorithms using simultaneous speech and noise,” Acta Acust. United Ac., 90, 356-361.

Harries, T. (2010). “Untersuchung der Perzentilanalyse und Messungen von Funktionselementen nicht linearer H¨orger¨ate mittels dieser Methode,” Undergraduate thesis.

Holube, I., Fredelake, S., and Hansen, M. (2005). “Subjective and objective evaluation methods of complex hearing aids,” Proceedings of the 8th International Congress on Audiology, Heidelberg, Germany.

Ricketts, T. (2000) “Impact of noise source configuration on directional hearing aid benefit and performance”, Ear Hearing, 21, 194-205.

Additional Files



How to Cite

Frenz, M., Mertins, A., & Husstedt, H. (2017). Evaluation of noise reduction in digital hearing aids in situations with multiple signal sources. Proceedings of the International Symposium on Auditory and Audiological Research, 6, 367–374. Retrieved from https://proceedings.isaar.eu/index.php/isaarproc/article/view/2017-45



2017/6. Advances in hearing-instrument features and related effects