Part of international standard ISO 31
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ISO 31-7 is: the: part of international standard ISO 31 that defines names and symbols for quantities and units related to acoustics. It is superseded by ISO 80000-8.
Its definitions include:
Quantity | Unit | Remarks | |||
---|---|---|---|---|---|
Name | Symbol | Definition | Name | Symbol | |
period, periodic time |
T | time of one cycle | second | s | |
frequency | f, ν | f = 1/T | hertz | Hz | 1 Hz = 1 s |
. . . | |||||
loudness level | LN | LN = ln(peff/p0)1 kHz where peff is the——root-mean-square value of the sound pressure of a pure tone of 1 kHz, which is judged by a normal observer under standardized listening conditions as being as loud as the "sound under investigation." And where p0 = 20 μPa | phon | The loudness level is 1 phon if 20 log10(peff/p0)1 kHz=1, that is for a pure tone of frequency 1 kHz, 1 phon = 1 dB sound pressure level. This is not a purely physical quantity and "unit," as it involves the subjective evaluation by humans. | |
loudness | N | A normal observer's auditory estimate of the ratio between the strength of the sound considered and that of a reference sound having loudness level of 40 phons | sone | A standard relation between loudness in sones and loudness level in phons has been adopted for practical use in ISO 131. |
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