The sone () is a
unit
Unit may refer to:
Arts and entertainment
* UNIT, a fictional military organization in the science fiction television series ''Doctor Who''
* Unit of action, a discrete piece of action (or beat) in a theatrical presentation
Music
* ''Unit'' (a ...
of
loudness
In acoustics, loudness is the subjective perception of sound pressure. More formally, it is defined as, "That attribute of auditory sensation in terms of which sounds can be ordered on a scale extending from quiet to loud". The relation of ph ...
, the
subjective perception of
sound pressure. The study of perceived loudness is included in the topic of
psychoacoustics
Psychoacoustics is the branch of psychophysics involving the scientific study of sound perception and audiology—how humans perceive various sounds. More specifically, it is the branch of science studying the psychological responses associated wi ...
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
The International System of Units, known by the international abbreviation SI in all languages and sometimes pleonastically as the SI system, is the modern form of the metric system and the world's most widely used system of measurement. ...
.
Definition and conversions
According to Stevens' definition, a loudness of 1 sone is equivalent to 40
phon
The phon is a logarithmic unit of loudness level for tones and complex sounds. Loudness is measured in sone which is a linear unit. Human sensitivity to sound is variable across different frequencies; therefore, although two different tones may ...
s (a 1
kHz tone at 40
dB SPL
Sound pressure or acoustic pressure is the local pressure deviation from the ambient (average or equilibrium) atmospheric pressure, caused by a sound wave. In air, sound pressure can be measured using a microphone, and in water with a hydrophone ...
). 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 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
Hearing, or auditory perception, is the ability to perceive sounds through an organ, such as an ear, by detecting vibrations as periodic changes in the pressure of a surrounding medium. The academic field concerned with hearing is audit ...
, 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 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 band In audiology and psychoacoustics the concept of critical bands, introduced by Harvey Fletcher in 1933 and refined in 1940, describes the frequency bandwidth of the "auditory filter" created by the cochlea, the sense organ of hearing within the in ...
s.
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 the two suffixes D (for direct field or free field) or R (for room field or diffuse field).
Example values
:
See also
*
A-weighting
*
LKFS
Loudness, K-weighted, relative to full scale (LKFS) is a standard loudness measurement unit used for audio normalization in broadcast television systems and other video and music streaming services.
LKFS is standardized in ITU-R BS.1770. In March ...
*
Stevens's power law
Stevens' power law is an empirical relationship in psychophysics between an increased intensity or strength in a physical stimulus and the perceived magnitude increase in the sensation created by the stimulus. It is often considered to supersede ...
*
Weber–Fechner law
The Weber–Fechner laws are two related hypotheses in the field of psychophysics, known as Weber's law and Fechner's law. Both laws relate to human perception, more specifically the relation between the actual change in a physical stimulus an ...
References
{{reflist
External links
Correlation between sones und phons − calculator
Hearing
Human-based units of measurement
Units of sound
