Affordable noise meter puts a number to the annoyance
30 Dec 2006 | 14:09 GMT
I started looking for a SPL -which technically stands for Sound Pressure Level- meter a few months ago and all I could find locally were expensive, high-end units above $200 greenbacks. Being the cheap b*stard that I am, I started looking on-line and lo and behold, I was able to find the CM-130 selling for around $50 at Amazon.com.
The CM-130 at a busy Buenos Aires intersection
This unit turned out to be easy to use, lightweight, and in short, everything I was looking for in an inexpensive, portable sound-meter, with some added surprises to boot. This unit sports a plus minus 2dB accuracy, which is more than enough for casual measuring. It runs on a standard 9V battery and comes with its own windscreen for accurate readings outdoors. The manufacturer claims that an alkaline battery lasts up to 50 hours of operation.
Cabbies help measure the ambient noise outside the INQ LatAm HQ
Below: street mural depicting the noise, one block away
The buttons are big and well placed in a vertical column, making finger mistakes virtually impossible. The text is also big and easy to read. The device operates in four "sliding ranges", 40 to 70dB, 60 to 90, 80 to 110 and 100 to 130dB. Since the 'range windows' are overlapping, when you hit a sound above the current limit, it's easy to press the "level" button and switch to the higher measuring range, without having to fear of an eventual off-range sound peak making you have to go back and forth between measuring ranges. In other words, in the real world, chances are that if you are in a street with 70dB of "ambient noise", the first measuring range of 40-70dB will show the legend "Over", telling you to switch to the higher measuring scale of 60 to 90dB. But while on this newer range, as it's an overlapping range with the previous one, chances are you will be able to measure varying degrees of noise, while also eventual periods of quietness below the 70dB average, without having to switch back to the first measuring range. You get the idea.
Close-up of the CL-130. Silence, I've heard of it!
Since I live in an apartment complex located at the intersection of two busy avenues, and one of which is a traffic route for ambulances on the way to a nearby hospital, believe me, street noise is ambient music in my flat. So the first thing I did was waiting for the noisiest time of the day, around 6:00pm, when the world+dog wants to return home, fast, and I decided to stick my thing out the window, and I mean the CM130!. What I measured was about 66dB of base noise, with the occasional spike of 70-75dB when cabbies started honking their horns due to the usual traffic jam which happens as a result of people crossing with a red light at the last minute. Oh, our half-Italian heritage at work!. At some point, when a pair of big-truck drivers decided to honk their horns, I measured 85dB, and that's from my 13th floor flat.
Noisy ancient Air Conditioner helps this correspondent stay cool
amid the Southern summer
The next step was measuring something more of interest to our geeky audience: computer hardware. But I faced a problem, the ambient noise never stopped. So, I had to reach for the only room in my flat that doesn't have windows: the bathroom. At 2am, and in complete silence, I put the CM130 in the 40-70dB range and started to measure notebook noise. But there was a problem: some odd unexplained spikes... it turns out the culprit was a wall clock, which was quickly put to death by removal of its battery. This device turned out to be very sensitive, and keep in mind you're measuring sound, any sound, so even heavy breathing can affect its readings. So, if you intend to use it to measure PC hardware noise, hold your breath for a second, and do your work in absolute silence to get accurate readings.
Stinkpad 380ED earns the 'noisiest junk' prize
Top: HD idle. Below: HD doing a defrag
The first PC put to test was my ancient Stinkpad 380ED from IBM. Its hard drive -specially seeks- is so noisy that someone might confuse it with a kitchen appliance. With the CM-130, I measured 45dB, just the drive spinning and its CPU cooler. Then, I started a defrag operation on its hard drive, just to get some nice seek noise ambient music. Then the readings went up five dB more to 50. In contrast, the trusty Gateway 7422GX with its Athlon 64 CPU and quiet hard drive scored less than 36dB in "stand by" mode -WinXP desktop loaded, no apps running or HD activity-, and starting a defrag operation made it jump only two dB to a 38 reading.
Gateway 7422GX is much quieter. Top: HD idle
Below: HD doing a defrag
The unit's fast/slow button helps get the average reading of quickly changing sound level patterns, and "Max hold" button is the icing on the cake, helping you leave the unit at any given location, press that button, then come back later and find out what was the highest sound reading by the device -it records the highest sound level peak and retains that info in the display, until you press it again to restore to normal mode.
The verdict
This unit 'does what it says in the box' and at an affordable price, to boot. Surely, there might be more expensive SPL meters out there for the connoisseurs. For the average geek wanting to compare sound levels of different noisy PC hardware, this one does the job. I give the CM130 four Fernandos in my one-to-five personal rating scale. Why not five? well, it doesn't make the drivers on the street more civil, nor does it quiet the sound of the horns and the construction work around me.µ
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