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Re: The Importance of Audio Measurements

Right before I read your post, I shared the following observation in a private e-mail to a fellow Propeller Head:


“So on the one extreme are those who uncritically accept DBT results and consider those who raise questions about the validity of such tests as 'ignorant'. On the other extreme are those who want the subject banned.

Pretty difficult to carry on reasoned discussions in that atmosphere.”

I probably should have added to that e-mail the statement that fortunately there are reasonable people on both sides of the objective-subjective divide who do seem willing to carry on a reasonable dialog.


In this regard, I was struck by the following comment in the Rowland piece:

Audio hardware and interconnect cables are sensitive to mechanical vibration (microphonics). Sound energy, transferred through structural and air mediums, can significantly impact the performance of all audio equipment in many domestic environments. Again, equipment sensitivity to this condition is rarely tested in manufacturing or considered during the design process.

The idea that microphonics could be responsible for audible effects in solid state electronics and cables has always struck me as fairly far-fetched. In fact, the miniscule levels of distortion some are attempting to measure in cables seems to me like it would be far below the threshold of human hearing. Yet to even raise the issue with them in a polite manner invites a tirade.

I was also struck by this part of the Rowland piece:

Among the most important tests for musical reproduction accuracy is the Fastest procedure developed by Audio Precision, Inc. This test will uncover wide band, dynamic nonlinearities in DUTs (devices under test) previously unexposed by twin-tone IMD (intermodulation distortion) and THD + N (total harmonic distortion plus noise) testing procedures. A composite of either 32 or 64 discrete tones, non-harmonically spaced throughout the 20 to 20 kHz bandwidth, is introduced to the DUT inputs. The DUT outputs are routed back into the computer interfaced analyzer, which sharply attenuates each of the 32 or 64 original tones. The resulting intermodulation (sum and difference) tones of the original tones are then integrated and displayed for analysis and/or continuing product development. Note that this test signal more accurately represents a musical signal due to its high content of discrete frequencies. Any nonlinearities present in the DUT directly create a multitude of spurious difference frequencies, which fall throughout the lower amplitude ranges of the entire audio spectrum, significantly limiting and compressing the usable dynamic range. A poor result on this test correlates to the common listening experience of dynamic range compression, congestion, loss of detail and obscuration of the silence and harmonic integrity in music as the material becomes increasingly complex.

On its face, this type of approach to measuring the performance of amps and preamps seems to make a lot of sense. But again, it seems to me that some extremist objectivists don’t even want to talk about things like this as they see it as a flight of subjectivist fancy, folly and mythology. On the other hand, some of those who are exploring measurements such as this, seem offended if they are asked how these measurements might relate to actual audible sonic differences.

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