|Fill in as many sound level boxes as necessary (max 10) and then click the calculate bar, to get the calculated sum. Provided, that each sound source has its own random phasing.|
A program to combine as much as thirty (30) noise sources
Conversion of sound pressure level to sound pressure and sound intensity
The ten octave bands of our hearing range
The formula for the sum level of sound pressures of n non-coherent radiating sources is
The reference sound pressure p0 is 20 µPa = 0.00002 Pa = 2 × 10−5 Pa (RMS) ≡ 0 dB.
From the formula of the sound pressure level we find
This inserted in the formula for the sound pressure level to calculate the sum level shows
LΣ = Total level and L1, L2, ... Ln = sound pressure level of the separate sources in dBSPL.
Non-coherent means: lacking cohesion, connection, or harmony. It is not coherent.
For example, adding three levels 94.0 + 96.0 + 98.0:
Table for combining decibel levels
Level difference between the two sound sources
Adding of equal loud non-coherent sound sources
Formulas: Δ L = 10 × log n or n = 10(ΔL/10)
Δ L = level difference; n = number of equal loud sound sources.
|n = 2 equally loud non-coherent sound sources result in a higher level of
10 × log10 2 = +3.01 dB compared to the case that only one source is available.
n = 3 equally loud non-coherent sound sources result in a higher level of
10 × log10 3 = +4.77 dB compared to the case that only one source is available.
n = 4 equally loud non-coherent sound sources result in a higher level of
10 × log10 4 = +6.02 dB compared to the case that only one source is available.
Adding (combining) levels of equal loud sound sources
|Simply enter the value to the left or the right side.
The calculator works in both directions of the ↔ sign.
The total level in dB is the level of one sound source plus the increase of level in dB.
Adding decibels of one-third octave bands to level of octave band
Combining decibels - adding up to thirty acoustic sound levels
How do Sound Pressure Levels add when listening?
|Example: The measurable noise of a motorcycle is at a certain distance
60 dB (A). How big is the total level of 4 motorcycles with the same volume?
Solution: 60 dB (A) + 10 log 4 = 60 + 6 = 66 dB (A).
If you are doing noise measurements of motorcycles you should at least consider the "honesty" of the dBA-readings without low frequencies.
|You can easily add up coherent and non-coherent sound level and sound pressure values. It is often desired to add the psychoacoustic perceived loudness or volume. See:|
|How many decibels (dB) level change is double, half, or four times as loud?
How many dB to appear twice as loud (two times)? Here are all the different ratios.
Ratio means "how many times" or "how much" ... Doubling of loudness.
|+10 dB||2.0 = double||3.16 = √10||10|
|+6 dB||1.52 times||2.0 = double||4.0|
|+3 dB||1.23 times||1.414 times = √2||2.0 = double|
|- - - - ±0 dB - - - -||- - - - 1.0 - - - - - - -||- - - - 1.0 - - - - - - -||- - - - 1.0 - - - - -|
|−3 dB||0.816 times||0.707 times||0.5 = half|
|−6 dB||0.660 times||0.5 = half||0.25|
|−10 dB||0.5 = half||0.316||0.1|
|Log. size||Psycho size||Field size||Energy size|
|dB change||Loudness multipl.||Amplitude multiplier||Power multiplier|
|Ratio||Change in Sound
Change in Sound
|Change in Sound
|20||+43.22 dB||+26.02 dB||+13.01 dB|
|15||+39.07 dB||+23.52 dB||+11.76 dB|
|10||+33.22 dB||+20 dB||+10 dB|
|5||+23.22 dB||+13.98 dB||+6.99 dB|
|4||+20 dB||+12.04 dB||+6.02 dB|
|3||+15.58 dB||+9.54 dB||+4.77 dB|
|2||+10 dB||+6.02 dB||+3.01 dB|
|- - - - - 1 - - - - -||- - - - ±0 dB - - -- -||- - - - ±0 dB - - - --||- - - ±0 dB - - -- -|
|1/2 = 0.5||−10 dB||−6.02 dB||−3.01 dB|
|1/3 = 0.3333||−15.58 dB||−9.54 dB||−4.77 dB|
|1/4 = 0.25||−20 dB||−12.04 dB||−6.02 dB|
|1/5 = 0.2||−23.22 dB||−13.98 dB||−6.99 dB|
|1/10 = 0.1||−33.22 dB||−20 dB||−10 dB|
|1/15 = 0.0667||−39.07 dB||−23.52 dB||−11.76 dB|
|1/20 = 0.05||−43.22 dB||−26.02 dB||−13.01 dB|
|Noise is annoying, harassing and unwanted sound. It is not a physical phenomenon, but
only mental processes change a sound to noise.
There are a number of definitions of noise. Important ones are:
1 - the acoustic ratio that characterize the noise and by measurable physical sizes, such as the amplitude or the sound pressure level, frequency, and the time behavior of the sound, can be described.
2 - the situational ratio, i.e. location, time and situation in which the person is situate during the occurrence of the noise, and the relation to the activities, intentions and the current being of the person who is exposed to the noise.
3 - the personal ratio of the person who is exposed to the noise, with their acquired cognitive and emotional implications for the sound source. The fact that noise is not
only dependant on physically measurable sizes, but "of more", makes the derivation of methods and calculation methods for the objective description to a problem and explains the problems of noise control, which are often found between the measured noise values and the perceived harassment.
Kurt Tucholsky wrote aptly: "Our own dog does not make noise, it only barks.
|Castrated sound level values in weighted dBA are added the same way like sound level values in unweighted dB.|
Pro audio equipment often lists an A-weighted noise spec – not because it correlates well with our hearing – but because it can "hide" nasty hum components that make for bad noise specs.
Words to bright minds: Always wonder what a manufacturer
is hiding when they use A-weighting. *)
Formulas for working with sound
|1 pascal (Pa) = 1 newton/m2
= 10 dyne/cm2
= 10 microbar
≡ 94 dB SPL (Sound Pressure Level)
Sound Pressure Level (SPL)
Sound pressure level Lp = 20 × lg (p / p0) in decibels (dB), where
p is the measured pressure as sound field size and
p0 is the reference pressure in the same system of units.
p0 = 20 micropascals or micronewtons/m2 = 0.00002 Pa
= 0.0002 microbar or dyne/cm2.
This reference pressure
p0 = 0.00002 Pa as a sound field size corresponds to a sound wave in free air with an acoustic intensity (energy) of I0 = 10−12 watt/m2 as a sound energy size.
Sound Intensity Level (SIL) or Acoustic Intensity Level
Sound intensity level LI = 10 × lg (I / I0) in decibels (dB), where
I is the measured intensity as sound energy size and
I0 is the reference sound intensity in the same system of units.
I0 = 10−12 watt per m2.