# Buying an SPL meter



## asdfLOL (Dec 21, 2010)

Hi

I'm a noob that is quite confused about SPL meters. I would like to buy a decent one so I can keep my audio under dangerous levels. I have read that the RadioShack meter does not read past 7khz, or something, which is bad because I think that even 128bit/s mp3's play up to 16khz and much higher with lossless formatting. I am looking for a budget meter that is trustworthy of my hearing!

Furthermore, what weighting should I use if I am trying to find the real spl to prevent hearing loss? I think wikipedia said that some weightings are used to curve with our hearing. Just because frequencies like 20hz and 19khz do not sound very loud I think they are just as damaging so I would not want to make them influence the reading of the meter to a lesser extent compared to midrange.

I like music, especially electronic a lot, and I tried to take great care of my ears; apparently that does not matter though because my brother who has been to concerts and blast 12' subs is unscathed but me rocking 20-30% ipod volume end up with constant ringing in the ears (I notice a trend with stuff like this in my life), very loud for my age too. I sleep to the sound of crickets or rain, and would like for this to be about 50db or less and play 70db music all day. Competing with the ringing depends on both frequency and volume which is why this is very important to me.

6AM and mp3 player is done charging, time for sleep and sorry any shortcomings in this rambling. I will check back tomorrow to clarify anything that doesn't make sense.


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## tonyvdb (Sep 5, 2007)

Hi and welcome aboard the Shack!

even though the radio shack meter is not as accurate above 7K its still fine for the use that you are planning for. another meter to look at is the Galaxy CM140 its a bit more accurate all around and can be found for around $120.
As far as weighting settings its recommended that you use the "C" setting and set it to slow response.


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## asdfLOL (Dec 21, 2010)

Are you very sure? From what I remember seeing they do not measure anything above 8khz, and clipping off half of the frequencies does not seem like a great idea. How inaccurate do they get for the higher frequencies? especially since I am going to be measuring them the most.

btw is there any other place to ask questions like this? like a site that specializes in SPL because this is one of the only ones I could find.


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## bambino (Feb 21, 2010)

Youv'e certainly come to the right place for your question. More folks will chime in with suggestions and ideas. I also know that Parts Express has one on sale untill the end of the month but what frequencys it will do is beyond me, there tec support is great though and would be able to answer your questions.:T


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## Wayne A. Pflughaupt (Apr 13, 2006)

Welcome to the Forum, asdfLOL!.

We often use SPL meters here at this Forum – at least certain models - for measuring frequency response of our home theater systems. However, it sounds like you intend to use one for its _intended_ purpose – measuring the volume levels of ambient sound or noise.

If that’s the case, you don’t need to be as concerned about the meter’s frequency response accuracy as much as its SPL accuracy – i.e., if you measure 78 dB, how close to an actual 78 dB is it?

There are four classes of SPL meters, the most accurate being laboratory-grade Class 0 meters that vary only ±0.4 dB. Naturally, those are very expensive. The most common and affordable meters are Class 3 meters such as the Radio Shack and Galaxy meters Tony mentioned, accurate to ±1.5 dB. Prices increase exponentially for Class 2 (±1.0 dB) and Class 1 (±0.7 dB) meters. For most nonprofessional applications, Class 3 meters are adequate.

The weighting scales (with A and C the most commonly used) are likewise just fine for the kind of measurements you’re interested in, keeping sound to a safe level for hearing protection. There’s no need to be overly concerned about not getting the ultra-high or ultra low frequencies reflected in the measurement. It’s long established that the frequencies most responsible for hearing loss are more-or-less in the mid range. So while accuracy at the frequency extremes might be important for measuring _frequency response_, it’s not necessary for the purposes of determining save volume levels. This is why they use the A-weighting scale for industrial noise standards, and it may explain why your “basshead” brother can still hear okay. 

On top of that, the highest and lowest frequencies in music, either live or reproduced with a sound system, are attenuated anyway. You can see this in the picture below. The second component from the top in the center stack is a real time analyzer that is displaying the frequency response of a CD that is playing. The horizontal row of red LEDs shows the 1/3-octave level the full audio spectrum, from 25 Hz (left-most LED) all the way up to 20 kHz (right-most). As you can see, response droops in the highest and lowest frequencies: Using the midrange as a reference, the signal is at 20 Hz is down 18+ dB at 25 Hz, and 16 dB at 20 kHz.







​


Re your 20-30% ipod volume, you can’t go by the volume setting you use. At any given volume, some headphones will play louder than others. I don’t know how well this would work, but you could try sticking the SPL meter mic right up to the headphone’s transducer and seeing what that measurement looks like. If all else fails, simply make a point to turn the volume up only a bit higher than is needed to adequately hear all the various instruments in the music.

Regards,
Wayne


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## Kal Rubinson (Aug 3, 2006)

asdfLOL said:


> Are you very sure? From what I remember seeing they do not measure anything above 8khz, and clipping off half of the frequencies does not seem like a great idea. How inaccurate do they get for the higher frequencies? especially since I am going to be measuring them the most.
> 
> btw is there any other place to ask questions like this? like a site that specializes in SPL because this is one of the only ones I could find.


How about this: http://www.realtraps.com/art_microphones.htm

Kal


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## tonyvdb (Sep 5, 2007)

The frequency response on the Radio shack or Galaxy meters are not a brick wall its just the accuracy drops down the higher you go. They will still read up to 20KhZ


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## Wayne A. Pflughaupt (Apr 13, 2006)

tonyvdb said:


> The frequency response on the Radio shack or Galaxy meters are not a brick wall its just the accuracy drops down the higher you go. They will still read up to 20KhZ


Don't forget that the RS meter (and most other Class 3 meters) are not designed for measuring frequency response, so our version of "accuracy" is not relevant to the intended function of the meter. "Accuracy" for a SPL meter is how closely its response tracks the reference weighting filters.

Regards,
Wayne


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## wdavidseidel (Jun 18, 2010)

I want to address your concern about hearing damage:

1. everybody's ears are different, some folks are more robust, others will be more sensitive to damage. The only way to find out is to take a resiliency test at an osha audiologist who screens workers at shipyards, etc. before they are hired.
2. ringing in the ears may or may not be caused by hearing loss but most folks with hearing loss will have ringing in the "missing" frequencies. google for more info on tinnitus.
3. play it safe: there are variations in the guidelines but most folks will agree, 
up to 85dBA average, up to 8 hours OK, 
up to 95 dBA average 2-4 hrs. are OK; 
exposed to more than 95 dBA average, limit exposure to 1-2 hrs.
never expose yourself to more than 105dBA, even for short periods.

Turn headphones down, do not drown out traffic noise, use earplugs in clubs.

Once the damage is done, there is no way to restore full function at this time. Take care of these precious instruments.


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