Minimum audible field and pressure measurements differ in listening conditions and calibration.

Evidence

By the 1930s, a number of scientists had made measurements of auditory thresholds at various frequencies. The data shown in Figure 2–9 are a compilation of these measurements adapted from Sivian and White (1933). These measurements illustrate the minimum detectable sound pressure level in dB SPL of young human listeners as a function of frequency when measured in the free field and over headphones. For the minimum audible field (MAF) measurements, sounds were presented over a loudspeaker (i.e., in the free field) and calibrated at a location 1 m away from the speaker. Note that for these free-field measures, the listeners were able to use both ears. For the minimum audible pressure (MAP) measurements, sounds were presented monaurally (i.e., to a single ear) over headphones, and measurements were based on a calibration reference level at the tympanic membrane. — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 243

Categorization

Category: Definitional Content

• DEFINE: Defines MAF vs MAP — free-field binaural measuring vs monaural headphone measuring — key concepts for the reader’s systematic understanding of hearing.

Related

• Hearing thresholds were first systematically mapped in the 1930s using two distinct measurement paradigms (similarity 0.92)
• The hearing threshold is measured from sounds reaching the subject’s binaural position. (similarity 0.88)
• Hearing’s lower limit is the minimum audible field; upper is pain (similarity 0.82)
• Two-ear listening improves sound-field thresholds by 10 to 15 dB (similarity 0.80)
• Free-field hearing thresholds can exceed headphone thresholds by over 15 dB (similarity 0.80)
• Free-field threshold testing yields thresholds 15 dB better than headphones (similarity 0.80)
• Sound amplitude is measured as root mean square pressure because ears sense pressure (similarity 0.79)
• Sound audibility depends on both its level and its frequency (similarity 0.79)
• Sound pressure level is the standard because it matches hearing (similarity 0.79)
• Absolute threshold is the minimum detectable sound level without external noise (similarity 0.79)
• Human hearing spans a 6.4-million-fold pressure range from faintest to painful (similarity 0.79)
• Hearing sensations correlate with stimulus magnitudes but only within the audible range (similarity 0.78)
• The 0 dB HL audiometric zero varies across frequency by design (similarity 0.78)
• Hearing detects pressure changes, not absolute ambient pressure (similarity 0.78)
• Ear sensitivity depends jointly on frequency and on sound level (similarity 0.78)