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How loud is this Decibel (dB) rating?

Decibel Level Approximations: dBSPL Source with Distance
180: Rocket engine at 30 m
150: Jet engine at 30 m
130: Threshold of pain
120: Jet aircraft taking off t 100 m; a Rock concert
110: Motorcycle accelerating at 5m; chainsaw at 1 m
100: Pnematic hammer at 2 m; inside a disco-tek
90: Loud factory; heavy truck at 1 m
80: Vacuum cleaner at 1 m; curbside of busy street
70: Busy traffic at 5 m
60: Office or restaurant inside
50: Quiet restaurant inside
40: Residential area at night
30: Theater, no talking
20: Rustling of leaves, only
10: Calm human breathing at 3 m
0: Threshold of hearing (human with good ears)

What does 1/2" ID, 3/8" ID or 1/4" ID mean?

I.D. stands for Inner Diameter. There are 3 standard measurements for a standard piece of tubing. Obviously there is the Length, but there is also the Inner Diameter and Outer Diameter.

The Outer Diameter is a measurement from the outside wall of the tubing, across the central axis of the tubing to the opposite outside wall. Basically look at the tubing end on, set a ruler on top of it, and measure the tube at its largest point. This measurement is less advertised and is only useful to you if you are using a system that has compression fittings or quick-connect fittings. Since the fittings fit overtop of the tubing, you need to know the outer diameter of the tubing.

The Inner Diameter is a measurement from the inside wall of the tubing, across the central axis of the tubing to the opposite inside wall. Basically look at the tubing end on, set a ruler on top of it, and measure the inner hole of the tub at its largest point. This measurement is extremely useful since almost all fittings have a barb that goes inside of the tubing. If the tubing is to large, the barb won't seal and leaks will be abundant. If the tubing is too small, it will be very difficult to fit it over the barb.

Note: All Innovatek products actually use 8 mm Inner Diameter tubing. This size is very close to 1/4" (6 mm) Inner Diameter tubing, so 1/4" tubing will fit over Innovatek barbs.

What is the coversion between Sone and Decibel (dB)?

This is a bit tricky to answer. The issue is that Decibels (dB) is an empirical measurement of the difference of sound pressure of two sounds. So to make standardized measurements of Decibels requires a room with a specific ambient sound pressure, a specific atmospheric pressure and a specific ambient temperature. This way Decibels provide the user with a reproducible experimental value that could then be experienced by the curious user. The Sone takes it a step further.

The Sone measurement is a numerical representation of a human's acoustic perception. This unit of perceived loudness was put into use after a proposal of S. S. Stevens in 1936. Since much of acoustics is important only in how humans react to the sound, it was seen fit that loudness be standardized. Loudness is a subjective measurement of the sound pressure, so one Sone was defined as equivalent to 40 Phons. Thereby one Sone equals the loudness of a 1 kHz tone at 40 dB SPL.

Now a Phon is also a unit of perceived loudness, but it is a subjective measurement of the strength (not intensity) of a sound. 1 Phon is defined to be equal to 1 dB SPL above the nominal threshold of hearing. The threshold of hearing is the sound pressure level (SPL) of 20 ┬ÁPa (micropascals), equal to 2 x 10-5 pascals. Once you start measuring other frequencies in Phons it departs from the Decibel but is related to it by the frequency weighing curve (equal-loudness contour) that reflects the frequency response of human hearing. The standard curve for human hearing is the A-weighted curve, in use when indicated by the dB(A) notation.

The human auditory system is generally sensitive to frequencies in the range of 20 Hz to 20,000 Hz. The human ear is most sensitive in the range of 1,000 to 5,000 Hz due to the biomechanics of the ear. The equal-loudness contour (Fletcher-Munson curve) is a representation of the measure of sound pressure (dB SPL) versus the Frequency for which a listener perceives a constant loudness. The loudness is measured in Phons and by definition two sine waves of different frequencies that have equal Phons are equally loud.

Back to the Sone, the number of Phons equal to 1 Sone was chosen so that a doubling of the number of Sones is perceived by a human ear as a doubling of the loudness of the sound. This also corresponds to increasing the sound pressure level by 10 dB. When you are dealing with frequencies other than 1 kHz, the measurement in Sones must be calibrated according to the frequency response of human hearing.

Without a specified frequency, it will be difficult to precisely reproduce the perception of the measured loudness from just the Sones value; but a value of 0.5 Sones could be reproduced by generating a 1 kHz tone at 30 dB. By definition that tone would be of equal loudness to a tone of any other frequency correctly measured as 0.5 Sones. The actual decibel measurement of different frequency tones that are rated at 0.5 Sones will vary in correspondence to the equal-loudness contour.

It is also important to note that Decibels, being a logarithmic measurement, means that the perceived loudness of 20 Decibels is twice that of 10 Decibels. For example, while a Rock concert might be rated at 120 dB, a Jet Engine rated at 150 dB is perceived as 8 times as loud as the concert. As the Decibel is in reality a measurement between two quantities, it is a dimensionless unit, like a percentage. This makes Decibel measurements not as useful as people often assume. To be useful, it should have been applied to the equal-loudness contour and have a specified distance.

Equally, the Sone should also be paired with a specified distance and should be matched with a suffix G to specify that it was calculated from frequency groups and also be notated by the suffix F (free field) or D (diffuse field). If the frequency groups are provided with the Sone measurement, along with the other values - it should be possible to accurately reproduce the measured loudness. Source: Wikipedia