Sound Converter — Decibel, Bel, Neper Converter
Convert between sound level units including decibel, bel, and neper. Also includes a frequency-to-wavelength calculator for sound waves in air. See also our Scientific Calculator and Data Transfer Rate Calculator.
How to Convert Sound Units
- Select the mode: sound level conversion or frequency-wavelength.
- For level conversion, enter the value and select the source unit.
- For frequency mode, enter the frequency in Hertz.
- Click Calculate to see all conversions.
Formula
Sound Level Conversions:
1 bel = 10 decibels
1 neper = 8.686 decibels
dB = 20 × log₁₀(V₁/V₂) for voltage/pressure
dB = 10 × log₁₀(P₁/P₂) for power
Frequency-Wavelength:
λ = v / f
Where: λ = wavelength (m), v = speed of sound (343 m/s at 20°C), f = frequency (Hz)
Period: T = 1 / f
Angular frequency: ω = 2πfExample
Convert 60 dB to other units:
60 dB = 6 bel (divide by 10)
60 dB = 6.908 neper (divide by 8.686)
Find wavelength of 440 Hz (concert A):
λ = 343 / 440 = 0.7795 m = 77.95 cm
Period = 1/440 = 2.273 ms
Common Sound Levels Reference Table
| Source | dB | Bel | Neper |
|---|---|---|---|
| Threshold of hearing | 0 | 0 | 0 |
| Whisper | 20 | 2 | 2.30 |
| Normal conversation | 60 | 6 | 6.91 |
| Vacuum cleaner | 75 | 7.5 | 8.64 |
| City traffic | 85 | 8.5 | 9.79 |
| Rock concert | 110 | 11 | 12.67 |
| Jet engine (30m) | 140 | 14 | 16.13 |
| Threshold of pain | 130 | 13 | 14.97 |
Frequently Asked Questions
What is a decibel?
A decibel (dB) is a logarithmic unit measuring the ratio between two values. In acoustics, it measures sound pressure level relative to the threshold of human hearing (20 micropascals).
What is the difference between dB and neper?
Both are logarithmic ratio units. Decibels use base-10 logarithms, while nepers use natural logarithms (base e). 1 Np = 8.686 dB. Nepers are more common in European telecommunications.
How does doubling sound intensity affect dB?
Doubling sound intensity adds approximately 3 dB. Doubling sound pressure (perceived loudness) adds approximately 6 dB. A 10 dB increase sounds roughly twice as loud to human ears.
What is the speed of sound?
The speed of sound in air at 20°C (68°F) is approximately 343 m/s (1,125 ft/s or 767 mph). It increases with temperature and varies by medium.
What frequency range can humans hear?
Humans can typically hear frequencies from 20 Hz to 20,000 Hz (20 kHz). This range decreases with age, especially at higher frequencies.