sone

The sone was proposed as a unit of perceived loudness by Stanley Smith Stevens in 1936. In acoustics, loudness is the subjective perception of sound pressure. Although defined by Stevens as a unit, it is not one of the SI units. Such units meet the stringent criteria of metrology, which include being realizable in a highly precise and reproducible manner, and so transferable for scientific and industrial purposes in a range of contexts.

According to Stevens' definition, the sone is equivalent to 40 phons, which is defined as the loudness level N_L of a 1 kHz tone at 40 dB SPL. The number of sones to a phon was chosen so that a doubling of the number of sones sounds to the human ear like a doubling of the loudness,^{[citation needed]} which also corresponds to increasing the sound pressure level by approximately 10 dB, or increasing the mean square sound pressure by a factor 10 (since due to the major property of logarithms for any given sound pressure level

the following holds: L + 10 dB = L + 10*1 dB = L + 10*log₁₀(10) dB = 10*log₁₀(p²/p0²) dB + 10*log₁₀(10) dB = 10*log₁₀((p²/p0²) * 10) dB). At frequencies other than 1 kHz, the measurement in sones must be calibrated according to the frequency response of human hearing, which is a subjective process. The study of apparent loudness is included in the topic of psychoacoustics and employs methods of psychophysics.

Loudness N in sones (for L_N > 40 phon):

or

Loudness level L_N in phons (for N > 1 sone):

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).

Examples of sound pressure, sound pressure levels, and loudness in sone

Source of sound	sound pressure	sound pressure level	loudness
	pascal	dB re 20 µPa	sone
threshold of pain	100	134	~ 676
hearing damage during short-term effect	20	approx. 120	~ 256
jet, 100 m distant	6 - 200	110 - 140	~ 128 - 1024
jack hammer, 1 m distant / discotheque	2	approx. 100	~ 64
hearing damage during long-term effect	6×10−1	approx. 90	~ 32
major road, 10 m distant	2×10−1 - 6×10−1	80 - 90	~ 16 - 32
passenger car, 10 m distant	2×10−2 - 2×10−1	60 - 80	~ 4 - 16
TV set at home level, 1 m distant	2×10−2	ca. 60	~ 4
normal talking, 1 m distant	2×10−3 - 2×10−2	40 - 60	~ 1 - 4
very calm room	2×10−4 - 6×10−4	20 - 30	~ 0.15 - 0.4
leaves' noise, calm breathing	6×10−5	10	~ 0.02
auditory threshold at 2 kHz	2×10−5	0	0

sone	1	2	4	8	16	32	64	128	256	512	1024
phon	40	50	60	70	80	90	100	110	120	130	140

Literature

• Stanley Smith Stevens: A scale for the measurement of the psychological magnitude: loudness. See: Psychological Review. 43, Nr. 5,APA Journals, 1936, pp. 405-416

See also

• sound pressure level
• Phon
• dB(A)
• Stevens' power law
• Weber-Fechner law

External links

• Conversion: Loudness N (sones) to loudness level L (phons) and loudness level L (phons) to loudness N (sones)