Interesting Papers re temporal resolution Options

[ncdrawl]

http://www.physics.sc.edu/kunchur/Acoustics-papers.htm

http://www.physics.sc.edu/kunchur/papers/FAQs.pdf

[Canar]

I just had a random thought about this and I wanted to run it by here:

The experimental procedure calls for a low-pass filtering of the signal. Does low-pass filtering significantly affect the perceived volume? Could the low-pass filter's effect on the perceived loudness be the perceived trait here? It is well-documented that decrease in loudness is perceived as decrease in quality. By slightly amplifying the filtered signal, could the perceived difference disappear?

So then, could the simple existence of the higher-order harmonics affect the overall power-spectrum (I'm aware that it will obviously be different in the frequency domain) significantly enough to be perceptible?

[andy_c]

Well, the 4.7us time constant does decrease the level of the 7 kHz fundamental by 0.18 dB, which he mentions in his paper. According to a description in his paper of another experiment (done by a different author), the just noticeable difference is 0.7 dB at that frequency.

This post has been edited by andy_c: Aug 4 2009, 03:40

[andy_c]

Here's another thing I noticed in his test apparatus. He describes the switching of the filter time constants and how it was optimized to minimize switching transients. He states that "...relays (which can induce a disturbance through magnetic flux change) were avoided...", although he does not say whether he tried any, and if so, whether this alleged disturbance was a problem in practice. The advantage of a relay would be to allow computer control of the switching, which when performed with the appropriate software, would allow for double-blind testing. IOW, it would allow for a test in which only the software, and not the test administrator, "knows" the state of the switch at any given time. He further states "...switch-bounce distortion was avoided by minimizing contact areas...", so this implies that a mechanical switch was used. Since that switch isn't a relay, it's just going to be a purely manual switching arrangement done by the test administrator physically flipping the switch. This in turn says that the test administrator is aware of the state of the switch at all times. It is therefore not a double-blind test. He does take care to call his tests "blind tests" rather than double-blind, so that is good. He uses the phrase "very effective blind listening tests" at one point in his article in fact. But he doesn't spell out what precautions, if any, were used to prevent the test subjects from observing the test administrator, which has the potential to influence the test results (AKA the Clever Hans Effect).

[Arnold B. Kruege...]

Here's another thing I noticed in his test apparatus. He describes the switching of the filter time constants and how it was optimized to minimize switching transients. He states that "...relays (which can induce a disturbance through magnetic flux change) were avoided...", although he does not say whether he tried any, and if so, whether this alleged disturbance was a problem in practice. The advantage of a relay would be to allow computer control of the switching, which when performed with the appropriate software, would allow for double-blind testing.

As a rule, relays don't induce significant disturbances in the signals they control when they change state. For example, one of the benchmarks for the ABX RM-2 relay module was an audibly transient-free switchover between two integrated amplifiers including phono or microphone input stages.

http://www.provide.net/~djcarlst/abx_rm2.htm

The production RM2 was based on reed relays with 5 volt coils, but its first adequate prototype (equally effective) was based on traditional open-frame, open-contact relays with 28 volt coils. Damping networks were placed across relay coils to prevent arcing and damage to the control circuits.

Transient free switching of audio gear is not always trivial, but the important issues are related to the actual oder and kind (NC or NO) of contact openings. The original Clark JAES article tells all.

Paranoia about relay contacts is just another high end audiophile straw man. Professional audio gear and communications equipment has been reliably switching audio signals with relays for over a century.