Computers Vs. the Real World

Now this is where the geeks have failed. By focusing on the Virtual Reality of their systems and ignoring the acoustical reality of said systems, they have seriously compromised their products and our musical capabilities. To be fair, many of them aren't even aware that their products are going to be used for audio and have made no effort to accommodate such use. However, Multimedia is all the rage now, and even generalist companies like Apple are busy touting 16-bit stereo sound. While it may be 16-bit, it sure doesn't give us the benefits of same, i.e. a dynamic range of 96 dB, directly due to computer/peripheral acoustical noise.

In the face of my audio adventure, I decided to get serious and make some reasonably formal acoustical noise measurements of various bits and pieces of computer gear I had lying around, plus one piece I borrowed. These include a Macintosh Powerbook 100, an Apple Quadra 650, a LaCie Tsunami 1.3 gB Hard Drive, an MDS Syquest 88 mB Removable Drive, a Leading Edge WinPro 486 PC, a Digidesign Expansion Chassis and a Studer/Dyaxis IMS dual drivbe storage system. I've identified them for reader information - not as a product evaluation. Please note that the Dyaxis unit is no longer made and that the Apple, Leading Edge, MDS and La Cie items were not designed for use in audio production work. Further note that my intent is not to bash any of these manufacturers. I believe that these performances are typical of all computer gear, and represent the state of the industry, not these manufacturers per se.

These measurements were all made at 18" from the front of the chassis, with some reverberant information included, but the unit decoupled from its work surface (a significant contributor to acoustical output). In the case of the Leading Edge 486 computer, it was measured from the bottom, through the open door of its enclosure in the desk. It may in fact be slightly softer than measured, relative to the others.

The softest of these items, the Powerbook 100, is 10 dB louder than my room. It is easily and annoyingly audible and has in fact busted audio takes when the drive spooled up during a voice-over, just in case you thinking I'm being picky-picky.

The loudest of these, the Studer-Dyaxis unit, is really annoying (21 dB louder than the room). Its acoustical emissions peak in the critical 4 KHz. region, really cutting into vocals and other critical timbral information.

The Digidesign Expansion Chassis (20 dB louder than the room) is slightly less offensive than the Dyaxis due to the fact that its primary output is at lower frequency and with less identifiable pitched content.

Below is a table that summarizes these considerations.

Device	dBA SPL	Typical Pro S/N ratio	Typical Home S/N ratio	Reduced S/N Ratio from ideal 96 dB	Reduction in range of my studio
Powerbook 100	38	52 dB	42 dB	78 dB	-10 dB
Quadra 650	39	51 dB	41 dB	77 dB	-11 dB
La Cie Drive	43	47 dB	37 dB	73 dB	-15 dB
MDS Drive	44	46 dB	36 dB	72 dB	-16 dB
486 PC	46	44 dB	34 dB	70 dB	-18 dB
Digidesign	48	42 dB	32 dB	68 dB	-20 dB
Dyaxis	49	41 dB	31 dB	67 dB	-21 dB

This isn't, unfortunately, the worst of it. Nobody uses these devices just by themselves. So we need to look at overall summed levels. Below is a table that shows various combinations in addition to the grand totals:

	dBA SPL	Typical Pro S/N ratio	Typical Home S/N ratio	Reduced S/N Ratio from ideal 96 dB	Reduction in range of my studio
Summed Power level of all Devices	53.8	36.2 dB	26.2 dB	72.2 dB	-25.8 dB
Summed Power level of Quadra & La Cie	44.5	45.5 dB	35.5 dB	71.5 dB	-16.5 dB
Summed Power level of Quadra, La Cie & Digidesign	50.3	39.7 dB	29.7 dB	65.7 dB	-22.3 dB

The results are disheartening: 54 dB SPL, the grand total for all of these devices running together, is a level that begins to approach the level of conversation! A professional studio might have a working signal-to-noise ratio of only about 36 dB, while your home studio might actually only have 26 dB, if you keep levels down to a point where the neighbors don't call the cops yet again. This in the face of the claimed spec of 96 dB signal-to-noise ratio!!!

Me? I've made a big investment in real estate and architecture just to gain peace 'n quiet where I work and the noise pollution generated by this equipment has reduced the quality of my effort by a factor of 20, right out of the box!