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The relationship between SPL and loudness of a single tone can be approximated by Stevens's power law in which SPL has an exponent of 0.67. [ a ] A more precise model known as the Inflected Exponential function , [ 3 ] indicates that loudness increases with a higher exponent at low and high levels and with a lower exponent at moderate levels.
While 1 atm (194 dB peak or 191 dB SPL) [11] [12] is the largest pressure variation an undistorted sound wave can have in Earth's atmosphere (i. e., if the thermodynamic properties of the air are disregarded; in reality, the sound waves become progressively non-linear starting over 150 dB), larger sound waves can be present in other atmospheres ...
A sound level meter (also called sound pressure level meter (SPL)) is used for acoustic measurements. It is commonly a hand-held instrument with a microphone . The best type of microphone for sound level meters is the condenser microphone, which combines precision with stability and reliability. [ 1 ]
A graph of the A-, B-, C- and D-weightings across the frequency range 10 Hz – 20 kHz Video illustrating A-weighting by analyzing a sine sweep (contains audio). A-weighting is a form of frequency weighting and the most commonly used of a family of curves defined in the International standard IEC 61672:2003 and various national standards relating to the measurement of sound pressure level. [1]
ISO equal-loudness contours with frequency in Hz. An equal-loudness contour is a measure of sound pressure level, over the frequency spectrum, for which a listener perceives a constant loudness when presented with pure steady tones. [1] The unit of measurement for loudness levels is the phon and is arrived at by reference to equal-loudness ...
Equal-loudness contours. 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 a human ear, they may be psychoacoustically perceived as differing in loudness.
The subject's absolute hearing threshold is calculated as the mean of all obtained thresholds in both ascending and descending runs. There are several issues related to the method of limits. First is anticipation, which is caused by the subject's awareness that the turn-points determine a change in response.
According to Stevens' definition, a loudness of 1 sone is equivalent to 40 phons (a 1 kHz tone at 40 dB SPL). [1] 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.