Head-related transfer functions are measured with in-ear microphones in anechoic chambers
Evidence
HRTFs or HRIRs are measured in free-field conditions with the sound source (a loudspeaker) placed in desired positions, for example, 2 metres from a subject at each azimuth and elevation angle of interest (Møller, 1992). An anechoic room can be used for the measurement, but the reflections from walls can also be eliminated by windowing the response to before the arrival of the first reflection. Small microphones are used to capture the response close to the entrance or inside the ear canal. In the former case, the ear canal is typically blocked by the microphone set-up, as illustrated in Figure 12.4a, or it can be kept open. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1410
Measurement of the HRTF for a listener is best carried out in an anechoic chamber to avoid unwanted sound reflections. A stereo recording is made with the microphones in the ear canals of the listener, who is asked to keep her/his head as still as possible. Usually a horizontal ring of loudspeakers at ear height is used where the angles of the loudspeakers are referenced to directly in front of the listener. A maximum-length sequence, or MLS, which is a pseudorandom binary sequence, is commonly used as the sound source to ensure that all frequencies are represented in the outputs. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 739
Categorization
- DEFINE: Explains the standard measurement procedure for HRTFs, the data underlying binaural and spatial audio.
- corroborated: 3 independent passages support this claim — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1410; David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 739
- XREF: connects to: Binaural microphones capture exact tympanum signals but depend on one’s own head shape; Large diverse datasets of human HRTF and ear geometry are now being collected; Outer and middle ear transfer function determines loudness across frequency. (+4 more)
Broader Connections
- Binaural audio reproduces ear canal signals from real or virtual scenarios.
#expands(0.80) — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1916