24 October 2007

What Does 30% Sound Like?

I came across an(other) unfortunate attempt at marketing "quiet." The company is an unquestioned leader in their industry. However, it would appear from this link that they should stick to what they know, which is sight and not sound. For those of you not versed in sound, a "30% reduction in sound," if correctly applied, results in about a 3 dB drop in relative sound pressure level. (Just put 0.7 into the equation that is the title of this blog, i.e., 10*log(.7²) = -3.1.)

As I see it, there are three possible ways this statement found its way into the release:

1. They came up with the percentage reduction by figuring the difference in decibels, which is wrong wrong wrong.

2. They came up with the percentage the right way, in which case Marketing might have said that 30% "looks better" than 3 dB. But, as any good acoustician will tell you, 3 dB is hardly worth marketing at all when you're talking about motor noise. As an example, most people wouldn't be able to tell much difference between a 36 dBA motor and a 33 dBA motor. (Not to mention that 3 dB lower is not even subjectively 30% quieter.)

3. They were simply given this number by someone (a motor supplier or ???) and Marketing ran with it. In which case, shame on all of them.

There is a fourth way, which would involve the subjective loudness scale (those oh-so-fun sones and noys). But I would be shocked if they "went there."

The motor in question is undoubtedly quieter than comparable or previous models - the company is reputable. My main point is that the statement of "30% reduction in sound" is ambiguous at best. So if anyone ever wants to know the reasons why I abhor using percentages when talking about sound, this blog post is a good place to start! :)

1 Comments:

Anonymous Jonathan Sheaffer said...

Savant-
Keep up the good stuff.
Enjoying each and every post!

Cheers, :)
Jon.

25 October, 2007 17:24  

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