A new standard, ISO TS 12913, provides an updated framework for designing restaurant dining spaces that mixes ambient sound, privacy and "at-my-table" speech intelligibility.

The standard includes the required use of binaural sound recording for room evaluation. Unlike a mono or stereo recording, a binaural recording is an immersive, 3D version that recreates for a future listener the experience of being in a room.

Acoustics consultant Klaus Genuit said the new guidelines for defining, measuring and evaluating soundscapes advance the effort to create audibly fine restaurants. He presented an application of the new ISO standard at a May meeting of the Acoustical Society of America.

Klaus Genuit photographed in an anechoic chamber with several loudspeakers to simulate a virtual acoustical scenery, as well as an artificial head for binaural recording. Credit: GenuitKlaus Genuit photographed in an anechoic chamber with several loudspeakers to simulate a virtual acoustical scenery, as well as an artificial head for binaural recording. Credit: GenuitGenuit said that while in the ideal classroom even a student at the back can hear the teacher, "it's quite the opposite in restaurant acoustics."

"I don't want to listen to the people at the table beside me, and I want to have acoustical privacy so they don't hear me." On the other hand, "you don't feel comfortable if it's too quiet," he said.

For a complex sound situation where there are a lot of sources, from tinkling cutlery to music and conversation, the selectivity of human hearing works only with binaural recording, he said. In 1986, he founded Head Acoustics by creating an artificial head, based on his doctoral research, with microphones in the place of ears to make binaural recordings.

The ISO guidelines also outline the analysis of the soundscape using psychoacoustics, which describes how a person perceives a sound, for example, as sharp or rough.

"This perception is dependent on the context," said Genuit.

A rough rumble sounds exciting if it's coming from a car at a NASCAR race, but not if it is coming from an air conditioner at a restaurant. Loud air conditioner noise is among the most annoying sounds in American restaurant soundscapes, according to Genuit.

The new ISO guidelines require acoustic consultants to learn from diners using a questionnaire to get a sense of their experience in the dining room.