Dummy head recording

In acoustics, the dummy head recording (also known as artificial head, Kunstkopf or Head and Torso Simulator) is a method of recording used to generate binaural recordings. The tracks are then listened to through headphones allowing for the listener to hear from the dummy’s perspective. The dummy head is designed to record multiple sounds at the same time enabling it to be exceptional at recording music as well as in other industries where multiple sound sources are involved.

The dummy head is designed to replicate average sized human head and depending on the manufacturer may have a nose and mouth too. Each dummy head is equipped with pinnae and ear canals in which small microphones are placed, one in each ear. The leading manufacturers in Dummy Head design are: Neumann, Brüel & Kjær, Head Acoustics GmBH, and Knowles Electronics.

The human perception of direction is complex:

Conventional music recording is produced for stereo playback which makes use of only Left and Right playback for speakers and headphones. The implementation of Dummy Head allows the recording artist to make use of three dimensional sound reproduction. This is because through playback via headphones the listener perceives sound as if they were in the position of the dummy. The recording is perceived through the pinnae of the dummy head.

There are two main methods used to create a binaural effect:

The main focus of recording with a dummy head is to achieve a perfect binaural playback that is suited to all listeners. The problem arises that each human head has different shaped and sized features. Due to the diversity in HRTFs it is impossible to create a binaural effect compatible for everyone’s ears. Therefore the simulated dummy head recording algorithm uses average HRTFs to create a moderate binaural effect for everyone.

The dummy head recording is associated with the use of the physical synthetic head called the “Kunstkopf”. The Kunstkopf would be placed in concert halls during the recording of a live orchestra or in the film industry actors could stand around the head whilst recording their dialogue. The dummy head could also be used to imprint positional information on prerecorded sound effects by playing sounds through a loudspeaker in a suitable orientation to the head. For example thunder and birdsong sounds to be played above the dummy head.

During the 1990s, electronic devices which used Digital signal processing (DSP) to reproduce HRTFs were made commercially available. These devices would allow the sound engineer to use dialled parameters to adjust the apparent direction of real time sounds. They were unusual and expensive, but would allow the sound engineer to alter special effects of prerecorded sounds quickly and conveniently. Through the manipulation of the parameters, sound engineers could take a monophonic recording of a passing car and make it sound as if it were passing behind them in real time. Recording with an actual dummy head for the same outcome would require a recording booth and a moving speaker, or an array of speakers as well as multiple panning or switching devices.

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Wikipedia