What does a sound pressure level of 90dB mean?

[Moof]

I have a piezo buzzer PK-35N29P. In the datasheet i found this:

sound preassure level (min) 90dB at 30 cm

What exactly means that???. 90dB is a realy big number, thats why i dont anderstand.

**broken link removed**

 

[flatulent]

Re: dB, newbie question.

0 dB SPL is 1e-12 Watts per square meter or 2e-5 Pascals of pressure variation. These are very low numbers and your 90 dB gives a milliwatt per square meter and about 0.6 Pascals of pressure.

 

[djalli]

dB, newbie question.

To add to flatulent, throughly:

You can convert to dB every kind of number, it helps because multiplication becomes addition and division becomes substraction.

Rule of thumb can be found here unless there is some other generality: http://www.sengpielaudio.com/calculator-soundlevel.htm

sound preassure level (min) 90dB at 30 cm

What exactly means that???.

Moof sound is an existing force if I may call it so. you never hear what is being said.

What it means is that the buzzer you got, at 30cm the force sound moving is 0.6 Pascals (in pressure) as flatulent said, more than 30cm you would expect a decrease on it. It is sound.

Pa unit is force per m^2. For your Buzzer rated at 90dB after 30cm, it means to a surface 1m^2 you get 0.6Newtons force.

 

[House_Cat]

Re: dB, newbie question.

There is a chart at the following URL that compares different everyday sounds. The sound pressure level of your buzzer at 30cm is about the same level of sound produced by a heavy truck or medium classical music.

**broken link removed**

 

[brmadhukar]

Re: dB, newbie question.

Hi,
Just to add to the previous explanations. dB always should be used for power, though you may use a variation (in such a case you use a relation ship of power).
B R M

 

[House_Cat]

Re: dB, newbie question.

dB always should be used for power, though you may use a variation (in such a case you use a relation ship of power).

Actually, the bel and decibel were put into use a Bell Laboratories as a way of expressing ratios that were too large to be conveniently written in other ways. The unitless notation is not restricted to only power ratios.

The bel or 1/10 bel (decibel) is used in many disciplines for expressing ratios other than power. In the question posted here (the field of acoustics) it is a sound pressure ratio - not power.

Earthquakes are measured on the Richter Scale which is in units of bel.

Electronic circuits use db notation for signal-to-noise (a voltage or current ratio - not power), or for expressing power ratios. Sometimes db is used just for comparison of large changes or relationships in a circuit.

A very nice discussion can be found at:

https://en.wikipedia.org/wiki/Decibel#History_of_Bels_and_Decibels

 

[Bob60]

Re: dB, newbie question.

Electronic circuits use db notation for signal-to-noise (a voltage or current ratio - not power), or for expressing power ratios.

Not only. Neper as well.
https://en.wikipedia.org/wiki/Neper