[Physics Class Notes] on Sone Pdf for Exam

The unit for measuring the quantity of sound pressure we perceive from the loud music is the Sone. 

While enjoying a late-night DJ party, we love to hear loud music and that music creates a lot of pressure on our ears. This loudness has some measurement and that measurements hold a unit with itself. The unit for the same is Sone. Sone is the comprehensive unit of loudness. 

On this page, we will learn about sones, the meaning of sone, and the types of sones in detail.

Meaning of Sone

Sones is a subjective unit of loudness. For an average listener, one sone equal to the loudness of a 1000-hertz sound that has an intensity of 40 dB, i.e., above the listener’s own threshold ability of hearing

So, basically, sone is a unit of loudness. Loudness is a subjective characteristic of a sound, as compared to the sound pressure level in dB, which is objective and easily measurable. Consequently, the sone scale of loudness is dependent on data achieved from subjects who were asked to distinguish among the loudness of pure tones and noise. One sone is arbitrarily set equal to the loudness of a 1,000-Hz tone at a sound level of 40 decibel above the standard normal or the reference level, i.e., the minimum audible threshold. A sound with a loudness of 3 sones is one that listeners perceive to be three times as loud as the reference sound.

One Sone

According to the definition given by Steven, a loudness of 1 sone is equal to 40 phons or a 1 kHz. The phon scale closely aligns with decibel, not with loudness, so the sone and phon scales are not proportionally related. Rather, the loudness in sones is, at least more of a power-law function of the signal intensity, with an exponent of 0.3, with this exponential value, every 10 phons (or 10 dB at 1 kHz) increase produces almost double of the loudness in sones.

Sone Definition And Conversions

Below is the table for the sone and phon conversion:

Sones Meaning

From the above table, we see that at frequencies other than 1 kHz, the loudness level in phons is calibrated according to the frequency response of human hearing ability through the set of equal-loudness contours, and then the loudness level in phons is matched to the loudness in sones through the same power law.

For the power law, loudness N in sones is LN, which is greater than 40 phons.

Where,

[N=left ( 10^{frac{L_{N}-40}{10}} right )^{0.30103} approx 2^{frac{L_{N}-40}{10}}] ….(1)

LN = 40 + 10 Log2 (N)….(2)

Here, the loudness level LN in phons for N is greater than 1 sone.

Sometimes, corrections are required at lower levels, near the threshold ability of hearing.

The formulas mentioned in equations (1) and (2) are valid for single-frequency sine waves or narrowband signals only. However, for multi-component or broadband signals, a more elaborative or expanded loudness model is required, accounting for critical bands.

To have a piece of precise information, a measurement in sones must be described in terms of the suffix G, where ‘G’ means that the loudness value is calculated from frequency groups, and by one of the two suffixes D, i.e., for direct field/free field or R, i.e., for room field/diffuse field.

Points To Note:

1. Sones are not decibels or volume or any other measuring units, it is actually a way to determine how sound is sensed. They are linear measurements similar to inches. Doubling the sone value means doubling the loudness (i.e. one to two, two to four is doubling the sound level in twice magnitude). Your 3 sone fan will be more than three times as noisy as a 0.9 sone fan.

2. One sone is equal to the sound of a quiet refrigerator in a quiet kitchen. Typically, the sone level is measured at the maximum speed of cubic feet per minute; however, some newly-launched products are also being tested at normal CFM settings to assure consumers with low sound level information.