There are actually a lot of audible effects that do not show up in measurements. To understand why we first have to briefly describe what measurements are. Unfortunately it is impossible to cover them all so we restrict to ourselves to the more common examples seen in Hifi literature.

Frequency responses charts is a form of measurements often used as “supporting evidence” when making these claims. To be pedantic, frequency responses are not strictly a measurement. They are a form of analysis derived from measurements. The distinction is important, as a frequency response chart can be derived from actual measurements, or simulated (i.e. calculated from a computer simulation). If you are comparing one chart from the other without knowing the origin then any conclusions drawn may be invalid.

The following is an example of a frequency response graph. The chart looks “Sciencesy", the red line looks pretty legit for some reason. The chart commands your attention, even more so when you have multiple charts on hand for comparison. They just do, this is a human reaction. People are naturally drawn to things of authority and charts have it all.

Few will realise:

• the X-Axis is not drawn to scale (logarithmic scale in this instance),
• the last X markers are also unlabelled (We assumed it to 40 kHz, but is it really?)
• Can we assume all the x labels before 1k are in Hz?

These issues showed how “the squiggly line” can be manipulated ever so subtly to have a misrepresentive visualisation.

What happens when we convert that authoritative chart into a table? Straight away the table has lost the superiority and legitimacy as we are far more accustomed to tables. It will also look  like so (Note i’m only showing a partial table, and the Sound Pressure are rough visual estimations):

Now we see this table for what they really are. The table effectively only tells you how loud each frequency is. We do not even know the source that generated these value pairs, are there really enough information for anybody to claim if it’s audible then it’s measurable? The reality is, nobody can do this reliability.

This blog post by JA from Stereophile is a good example of how something that effectively measures the same, can sound different : Link.

A comment by “cgh” in an online reprint of a Stereophile review caught my attention: “The [1990s] were probably the last real decade that we could reasonably bend the truth. Everything since is verifiable electronically.”

Everything? After a quarter century of measuring the performance of audio components for this magazine, I’m not so sure that we have a firm handle on what makes audio products sound different from one another.

The above blog is a good read and I suggest everybody do so as JA can and has explain it a lot better than I have.

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