Volume and distance

[Justynfromnz]

Hi there...Im not very flash with the old physics , and im not sure if this is the right place to post this , Buuuuut...

I was wondering, if a speaker was playing a 440hz tone (sine) , measured at 50 Db at the speaker , how far away would you need to be before an average persons ear couldn't hear it? Ive ben trying to look at various graphs and calculator thingies online but can't seem to work it out. I am assuming the distance travelled is also frequency dependent. Is this correct? Im just doing some basic plans for an installation ( arty type, not PA) and seeing if an idea i had is viable. Thanks for your help. justyn

[Les]

Justyn.

For free space and an omnidirectional source sound intensity falls off as inverse square and sound pressure (or particle velocity) falls off as inverse.

The trouble with this is you are probably not in a free space evironment and the radiator is probably not omnidirectional. In a room you would have to know a lot of acoustic details to calculate anything meaningful.

What are you trying to do.... set things up so the system noise level is at the threshold of audibility at the listening position?

Les
L M Watts Technology

[Justynfromnz]

Hi there
thanks for that...
Im trying to play say, 4 little pieces (pre recorded with movies) outside,
at a moderate volume and wondering how far apart they need to be to not be heard when standing in front of a different one...

[tINY]

People will key on the one in front of them - so it's not as big an issue as you might think. Directional speakers can help you if you can direct the sound away from other installations.

Shy of renting narrow beam horns, as far away as you can comfortably get them is as good as you can do if you don't have any trees, shrubs, or walls to work with.




-tINY

[nosebleedaudio]

Everytime you double the distance you loose 6dB SPL.

[Justynfromnz]

Ah brilliant
thanks

[ghostcake]

Originally Posted by Justynfromnz

Hi there...Im not very flash with the old physics , and im not sure if this is the right place to post this , Buuuuut...

I was wondering, if a speaker was playing a 440hz tone (sine) , measured at 50 Db at the speaker , how far away would you need to be before an average persons ear couldn't hear it? Ive ben trying to look at various graphs and calculator thingies online but can't seem to work it out. I am assuming the distance travelled is also frequency dependent. Is this correct? Im just doing some basic plans for an installation ( arty type, not PA) and seeing if an idea i had is viable. Thanks for your help. justyn

this may help
Peak SPL Calculator

Originally Posted by nosebleedaudio

Everytime you double the distance you loose 6dB SPL.

i may be missing something here, but wouldn't double the distance mean you would lose 3db not 6 because an increase of 3db means signal output is doubled?


Edit: nvm, you are correct.