Turn adverse acoustics into favourable dynamics

March 7, 2016 by Marco Di Manno
mauvaise condition accoustique
“Echo” is a complaint often reported by hearing aid users. But what these individuals are experiencing in most situations is reverberation, not echo. The two are very easily confused.

The difference between echo and reverberation

Echo is the reflection of sound over a long distance, for example, cliffs, canyons, and other large open spaces. Reverberation is the reflection of sound off nearby obstacles, such as walls, windows, and ceilings. There are some very clear acoustical differences between echo and reverberation.

Echo

We are talking about echo when:

  • The reflected sound returns to the sound source in > 0.1 second
  • The memory of the original sound is lost
  • The perceived sound is recognized as a whole new listening experience

In many situations, people intentionally create echo. If they want to enjoy the full experience of this sound, it obviously won’t be in their best interest to dampen or remove it.

Reverberation

We are talking about reverberation when:

  • The reflected sound returns to the sound source in < 0.1 second
  • The memory of the original sound is good
  • The original and reflected sound are perceived as one prolonged event

Reverberation can happen in everyday situations, and it becomes bothersome when it affects the person’s ability to understand speech.

Reverberation is a physical phenomenon that occurs in many listening environments. Small living rooms with furniture and curtains have a limited amount of reverberation. Huge buildings such as halls or cathedrals have more. The perceived amount of reverberation depends on the acoustics (determined by room size and surface reflection) and the distance from the speaker to the listener.

The impact of reverberation for hard-of-hearing people

In highly reverberant conditions, reflection can be a detrimental signal like noise. It can have a negative impact on speech intelligibility and listening comfort. This is more noticeable for people with a hearing loss, even when they are wearing a hearing aid.

Reverb Reduction is an algorithm that first detects the reverberant part of the signal and its specific characteristics. It then attenuates this part of the signal while preserving important speech information. The system is always active and able to estimate the likelihood of reverberation. This reduces the perceived amount of reverberation and improves listening comfort.

Reverb Reduction can be used in conjunction with other hearing aid settings and programs to help tailor hearing aids to each user’s unique hearing and lifestyle needs.

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