Cocktail Party Environment

Think about a crowded pub, a restaurant or a reception where you have to carry on a conversation amidst several types of disturbances such as

  • loud music in the background
  • loud machine or traffic noise
  • a number people around you that have a conversation among each other

Apart from the background noise other disturbances might hamper conversation :

  • room reverberation : in highly reverberating (reflecting) rooms many delayed and attenuated copies of the same sound signal will arrive at the listener's ear stemming from reflections against walls and objects in the room. As a consequence, the signal will sound reverberated, i.e. echoed. In the case of a speech signal, it will in general be harder to understand what is being said.
  • feedback : due to the fact that hearing aid loudspeaker and microphone(s) are close together, feedback can occur, giving rise to a disturbingly loud tonal signal in the device. Feedback does not occur in cochlear implant systems.

As far as the background noise is concerned, several types can be distinguished :

  • directional noise is a type of noise that mainly reaches the ear from one direction in space, and that therefore easily can be localized based on pure auditive information. Example : a television or a radio in a living room.
  • diffuse noise reaches the ear from many directions in space, and is therefore very hard to localize auditively. Diffuse noise occurs in highly reverberating environments, or stems from large-size noise sources that are not well confined in space. Example : engine and wind noise inside a car cabin.
  • babble or cocktail party noise is a mixture of many human voices as produced during a cocktail party or a reception, as shown in the figure above.
  • stationary noise is a noise whose characteristics (mean amplitude level, frequency content, ...) are constant, i.e. not changing or fluctuating as a function of time. Example : noise from a ventilator.
  • non-stationary or fluctuating noise has time-varying characteristics. Example : cocktail party noise.