db meter?

Radio Shack sells one for $60, claims accuracy of 2 dB at 114 dB. It's pretty hard to measure sound pressure level more accurately than that outside of an anechoic chamber.

$49 and change in our neck of the woods. And yes, it is pretty accurate... or at least reproducible. We use ours to measure the sound pressure of salutes. The digital version has a sample-and-hold feature we need for peak readings.

LLoyd

The measurements you are planning to take for the freeway people are not easily done with a common sound level meter. The preferred method is to measure LEQ ,the time averaged sound level, over a 24 hour period. Usually another 8 hour LEQ measurement is taken during hours of sleep for a residential community and then combined. Also the weighting of the measurement (A,B or C) has to be taken in account. Sometimes frequency specific measuremets are also taken.

Here is a very basic prediction of sound level attenuation for a wall separating a sender from a receiver, if the receiver is much further away from the wall then the sender. Height of wall squared /( wavelenght of frequency, times ,distance from wall to sender). This gives a number which then is plotted on an estimating chart. For a calculation result of .5 the attenuation is 5 db For a result of 1 the attenuation is 10 db For a result of 2 its 12db For 4 its 16 db For 6 its 18 db For 10 its 20 db For 20 its 23 db For 30 its 25 db For 100 its 30 db, and that is the theoretical limit. In practice more than 25 db attenuation is unheard of.

cheers T.Alan

I'm hearing (no pun intended) that if I want cheap buy the Rat Shack digital SPL meter. I'll probably do that. And I'm not trying to really outdo a pro tester, I just want some data when I go object to their not raising my sound wall. I know a guy who did this a long time ago (he was one of my dad's coworkers) and he used a handheld meter to get data from his front porch and he said it was very effective at the time. Thanks to all.

GWE

T.Alan Kraus wrote:

On Fri, 16 Sep 2005 10:44:30 -0700, with neither quill nor qualm, Grant Erwin quickly quoth:

Yeah, grab one off Ebay for less than half the new price, delivered.

I ended up buying that JOAT meter after all. (VOM, humidity, sound, light, capacitance meter rolled into one rubberized case with nice padded carrying case for $75 delivered. I haven't had a chance to check the cal on it but it gives identical wall outlet readings to my super-duper $5 HF/Chiwanese DVM.) I like it! Mastech S8209.

I keep forgetting to see how the dog barking registers on the meter above the freeway noise but it cuts through walls and double-paned windows like a hot knife through butter. The mutt has been fairly quiet lately. I-5 runs downhill about 1/2 mile away from my house and the truck traffic can be overwhelming sometimes. Especially when a convoy of unmuffled jake brakes go by, all farting in unison.

Salutes.. fireworks?

John

Grant - those can be leased - you want a dbA for audio - Maybe there is a leasing company that will 'dump' a unit due to downsizing.

Martin Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH, NRA Life NRA Second Amendment Task Force Charter Founder

Grant Erw> Anyone got a clean db meter they don't need and want to sell/trade? I

Grant,

There are a bunch of real SPL meters on ebay cheap. You want to make sure the one you get comes with a microphone, as these were usually plug ons. You might look for a General Radio or Bruel and Kjaer. Simpson made them too.

Kevin Gallimore

I have never seen one with a remote readout. Some have a data output which presumably could be fed to an external display. Most have an analog output to drive a chart recorder. The analog output could be fed to a comparator that could eventually turn on a light at a preset sound level, warning the partyers.

Kevin Gallimore

axolotl wrote: The analog output could be fed

Forgive me for answering my own post. A better idea would be to use the comparator output to kill the power to the amplifiers.

Kevin Gallimore