The 10 Best Decibel Meters
Pressure Through The Air
That's your body acting as a crude decibel meter, since 120dB is the threshold of pain in the ear.
A decibel, though, is a measure of the pressure with which a source emits sound, which bears only a minuscule impact on the sound's frequency.
Understanding how a decibel meter works is only half the battle when evaluating the safety of a space for human hearing. The other half requires that we understand the scale on which these meters place their measurements. The decibel scale is logarithmic rather than linear, which means its units increase by powers of ten.
For example, where 20 inches on a ruler is only twice that of 10 inches, on a logarithmic decibel scale 20dB (the shorthand for decibels) is ten times the sound intensity of 10dB–but what exactly are decibels?
We know that sound waves are vibrations in the air, and that they resonate in our ears where a complex system of bones and nerve endings translates those vibrations into the signals our brains interpret as sound. We also know that the frequency of those waves has a direct effect on their pitch.
A decibel, though, is a measure of the pressure with which a source emits sound, which bears only a minuscule impact on the sound's frequency. The meters on this list utilize microphones that are especially sensitive to pressure, and they convert that into a decibel reading.
That 10dB readout is pretty close to the threshold of human hearing (which, by the way, is 0dB). 20db is about what you'd hear from a ticking clock. A loud conversation would register around 50dB, and loud highway traffic around 80dB. From there we get into ranges that pose a threat to human hearing.
Above 85dB for at least eight hours can cause hearing damage. Above 100dB for a mere 15 minutes will do the same. Anything above 120dB, and you can suffer damage immediately. Ever been at a loud concert and actually felt pain in your ears from it? That's your body acting as a crude decibel meter, since 120dB is the threshold of pain in the ear. Bring some ear plugs next time.
Turn That Music Down
It's easy to dismiss somebody for complaining that the band is playing too loudly. He or she is just too sensitive or "getting old" (for the record, I started remarking about this when I was 15). If I'd had one of these decibel meters at the ready, I could have easily proved it.
While measuring sound levels for their potential to cause harm to human hearing is important, I would have used one of these meters slightly differently. After all, pretty much any instrument in the room would have registered as a threat to human hearing, and I spent enough nights falling asleep to a bombastic ringing in my ears to know I'll probably be deaf by the time I'm 60.
If you look at the mix above, you'll see that the drums and vocals get buried behind a wall of distorted chords created by the egomaniac guitarists.
What I wanted to quantify was more nuanced. I would have used the decibel meter to measure the specific output in different corners of the room from each individual instrument. That means I'd collect data on the vocals coming through the PA system, the guitars screeching through their half-stacks, the bass as it pumped along, and, of course, the drums.
I've heard enough bands in enough concert halls to know what the results would have been. The guitars would have registered close to 120dB, the vocals at around 110dB, the bass at roughly the same, and the drums anywhere between 100 and 120dB, depending on the quality of the kit and the force of the drummer. Recall the logarithmic explanation above to realize how broad a range of loudness this is.
Ask any audio engineer and they'll tell you that the two most important elements in a rock mix are the vocals and the drum pocket (bass drum and snare drum). If you look at the mix above, you'll see that the drums and vocals get buried behind a wall of distorted chords created by the egomaniac guitarists. It's awful for the live experience, and it's even worse for your hearing.
So, sure, you can grab one of these decibel meters to determine the safety of a given sound environment. That's what they're designed to do. But I'd encourage any musician reading this to get one into your practice space, to soundcheck with one of these meters, and to keep you stringed instruments and keys turned down below the natural levels of the drums and vocals. You'll be surprised how much better it all sounds.
Eliminate The Ear
The earliest government-sanctioned tests for the loudness of a space took place in 1929, when the New York Noise Abatement Commission gathered data on noise levels throughout New York City. These early detection and measurement methods relied on a device the technology for which came out of early telephone development, and it actually produced noise rather than taking it in to measure it.
An operator would raise the level of intensity put out by the device until it roughly matched that of the environmental sounds, judging the equivalence with his ear. Not only did this method rely heavily on the subjective senses of the individual tasked with measuring the sounds, it also added sound to the environment, inevitably muddying the discovery.
As microphone technology improved in the music industry, the sensitivity and accuracy of pressure-sensitive ribbons and diaphragms led to their incorporation into sound level pressure measurement. Still, those devices were only accurate to within several decibels, and their readouts couldn't be as specific as to display tenths of decibels as today's much more refined technology can do with ease.