The sone ( / ˈ s oʊ n / ) is a unit of loudness , the subjective perception of sound pressure . The study of perceived loudness is included in the topic of psychoacoustics and employs methods of psychophysics . Doubling the perceived loudness doubles the sone value. Proposed by Stanley Smith Stevens in 1936, it is not an SI unit .
8-464: According to Stevens' definition, a loudness of 1 sone is equivalent to 40 phons (a 1 kHz tone at 40 dB SPL ). The phons scale aligns with dB, not with loudness, so the sone and phon scales are not proportional. Rather, the loudness in sones is, at least very nearly, a power law function of the signal intensity, with an exponent of 0.3. With this exponent, each 10 phon increase (or 10 dB at 1 kHz) produces almost exactly
16-467: A doubling of the loudness in sones. At frequencies other than 1 kHz, the loudness level in phons is calibrated according to the frequency response of human hearing , via a set of equal-loudness contours , and then the loudness level in phons is mapped to loudness in sones via the same power law. Loudness N in sones (for L N > 40 phon): or loudness level L N in phons (for N > 1 sone): Corrections are needed at lower levels, near
24-442: A human ear, they may be psychoacoustically perceived as differing in loudness. The purpose of the phon is to provide a logarithmic measurement (like decibels ) for perceived sound magnitude, while the primary loudness standard methods result in a linear representation. A sound with a loudness of 1 sone is judged equally loud as a 1 kHz tone with a sound pressure level of 40 decibels above 20 micropascals. The phon
32-402: Is psychophysically matched to a reference frequency of 1 kHz. In other words, the phon matches the sound pressure level ( SPL ) in decibels of a similarly perceived 1 kHz pure tone. For instance, if a sound is perceived to be equal in intensity to a 1 kHz tone with an SPL of 50 dB, then it has a loudness of 50 phons, regardless of its physical properties. The phon
40-502: The Acoustical Terminology standard ANSI/ASA S1.1-2013 . Because the phon is a unit associated with a subjective percept, it is obtained by presenting the considered sound to a group of normal-hearing human listeners and by taking the median of the loudness levels they report. Such measurements have been performed for known sounds, such as pure tones at different frequencies and levels. The equal-loudness contours are
48-410: The threshold of hearing. These formulas are for single-frequency sine waves or narrowband signals. For multi-component or broadband signals, a more elaborate loudness model is required, accounting for critical bands . To be fully precise, a measurement in sones must be specified in terms of the optional suffix G, which means that the loudness value is calculated from frequency groups, and by one of
56-399: The two suffixes D (for direct field or free field) or R (for room field or diffuse field). Phon The phon is a logarithmic unit of loudness level for tones and complex sounds. Loudness is measured in sones , a linear unit. Human sensitivity to sound is variable across different frequencies ; therefore, although two different tones may present an identical sound pressure to
64-554: Was proposed in DIN ;45631 and ISO 532 B by Stanley Smith Stevens . By definition, the loudness level in phons of a sound is the sound pressure level (in dB SPL ) of a 1 kHz pure tone that is judged as having the same loudness . The phon unit is not an SI unit in metrology. It is defined as a unit of loudness level by the American National Standards Institute in
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