Low cost sound level meter?
Salmon Egg
I have seen some low cost items, circa $50US on eBay. Are any of these
good enough. I am not ready to spend an order of magnitude more for a
B&K or similar item.
My main questions for the cheap ones would be:
1. Can they hold peak value for sounds that last for a few tenths of a
second?
2. How can these be calibrated?
I can see how the inverse square law can be used to check the linearity
of the dB scale, but getting an absolute calibration looks like it can
be troublesome.
Bill
--
An old man would be better off never having been born.
Ethan Winer
They also offer an SPL meter calibrator that claims 0.5 dB accuracy
and seems to work with other brands of SPL meter. I have no idea if
these products are excellent or terrible.
--Ethan
GregS
A digital meter will tend to provide better short peak levels, but
it all depends on the circuitry. There must be some kind of standard
here someplace regarding speed.
greg
answerman
B20E98.101...@news60.forteinc.com:
> I would like to get a sound level meter for recording dig barking
level.
> I have seen some low cost items, circa $50US on eBay. Are any of these
> good enough. I am not ready to spend an order of magnitude more for a
> B&K or similar item.
>
> My main questions for the cheap ones would be:
>
> 1. Can they hold peak value for sounds that last for a few tenths of a
> second?
If you really mean peak, and I doubt that you do, you need a meter that
has peak detection/hold capability, and you aren't going to find one on
eBay for $50. Before you buy anything you need to determine whether you
need peak detection/hold, or RMS detection with max hold. It all depends
on exactly what you are trying to measure and why.
> 2. How can these be calibrated?
Only by someone with the equipment and knowledge. If you need a NIST
traceable calibration, then only by a calibration lab.
Salmon Egg
answerman <answ...@home.com> wrote:
> If you really mean peak, and I doubt that you do, you need a meter that
> has peak detection/hold capability, and you aren't going to find one on
> eBay for $50. Before you buy anything you need to determine whether you
> need peak detection/hold, or RMS detection with max hold. It all depends
> on exactly what you are trying to measure and why.
My main intended use would be to measure dog barking. Certainly, the
annoyance of barking is not the average power. It would be more
associated with maximum of a bark and the frequency spectrum.
Angelo Campanella
"answerman" <answ...@home.com> wrote in message
news:deadnXlObKRN7qrR...@giganews.com...
> Salmon Egg <Salm...@sbcglobal.net> wrote in news:SalmonEgg-
> B20E98.101...@news60.forteinc.com:
>
>> I would like to get a sound level meter for recording dig barking
> level.
>> I have seen some low cost items, circa $50US on eBay. Are any of these
>> good enough. I am not ready to spend an order of magnitude more for a
>> B&K or similar item.
The Radio Shack 33-2055, digital sound level meter, suits and is about
$50 (their web page) these days. That meter has some inconveniences such as
manual range switching. A repetitive scenario is required to affirm your
range setting in order to get a credible reading. Each range, 20 dB in
width, is stepped every 10 dB from 60 to 120 dB.In your case, this requires
a dog that will bark several times on command and with a consistent
level.... Another disadvantage is that it displays sounds only above 60
decibels.
The range situation for barking is troublesome... I just tried it by me
'barking' at the meter.... The held maximum will display a number, such as
70 dB (60 dB scale) even though the maximum value or peak was above that.
Resetting it to the "70" scale produced a max value of "80" (I don't bark
consistently), so I should have to reset the scale to "80" and try again,
etc... The value so obtained and displayed is only either Slow or Fast; no
"Impulse" and no true "peak settings". So you end up with a measurement that
is not really "peak"....
>> 1. Can they hold peak value for sounds that last for a few tenths of a
>> second?
Yes... read the manual carefully, page 14. You need to decide whether
you want the Maximum found for Fast or Slow response.
When the 33-2055 is run in the DH mode, you trigger it on and then off
(or set it to average for several seconds). After "off" is done, the memory
contains the average (Leq), the Min and the Max... holding all three as long
as you like. But it must be written down before proceeding to another try or
another measurement.
> If you really mean peak, and I doubt that you do, you need a meter that
> has peak detection/hold capability, and you aren't going to find one on
> eBay for $50. Before you buy anything you need to determine whether you
> need peak detection/hold, or RMS detection with max hold. It all depends
> on exactly what you are trying to measure and why.
Granted, the 33-2055 is not a Type 1 instrument, but it is a useful
estimate for many situations. There is no peak setting, so you are left with
but an estimate of barking dog transient sound levels in the end...
>> 2. How can these be calibrated?
Out of the box, I have found these to be within about one decibel. There
is a tiny adjustment screw for the situation where you have access to a
calibrator. But that should be done with signals of more than one frequency.
250 Hz and 1,000 Hz calibrators are common, each with their unique dB level.
> Only by someone with the equipment and knowledge. If you need a NIST
> traceable calibration, then only by a calibration lab.
Agreed
>> I can see how the inverse square law can be used to check the linearity
>> of the dB scale, but getting an absolute calibration looks like it can
>> be troublesome.
Correct, outdoors over the ground will be a very poor environment. There
is always some residual reflection from that ground, even when covered with
a sound absorber. You need a fully anechoic environment to experience
anything like an accurate 6dB/dd result sound environment
Ange