Occam's Razor: The Signal to Noise Ratio

Signal to noise can apply to all waveforms, not just electrical. Perhaps emphasizing the term waveform rather than signal would be helpful.  I regard them as synonymous.

In the analog audio world, the signal exists as a waveform. The original acoustic waveform hits a microphone that transduces this acoustic signal into an electrical waveform. For recorded music, this electrical waveform is then transcribed into bits in the digital world, a physical groove on a record, magnetic energy on a tape. Our various devices (DAC, phono cartridge, tape head) convert this stored version back into an electrical waveform. We diligently maintain the purity, accuracy, integrity of this electrical waveform with equipment topology, vibration isolation, electrical isolation with dedicated circuits, fiberoptic cables, cable hygiene, and power conditioners.  Anything that adds, subtracts, disrupts, distorts, colors or otherwise interferes with the original waveform can be considered to lower the integrity of the original waveform/signal, either by increasing the noise or decreasing the signal. The best audio system in the world cannot leave the original electrical waveform unchanged. The electrical SNR always suffers, but the better the system, the less the damage. You know the advertising terms, “vanishingly low distortion” and “highest signal to noise ratio”. Otherwise known as retaining the original waveform.

This electrical waveform that our sources have recreated ultimately reach our speakers and are transduced back into an acoustic waveform. It includes waveforms associated with the fundamental wavelengths of the instruments and voices and their harmonics, the resonances and related acoustics of the recording space and even the occasional contribution of a cough or a truck rumbling by. These all comprise the waveform/signal coming out of the speaker.  At this point, the signal can be regarded as having a very high acoustic SNR since there is no acoustic noise (distorted waveform) yet associated with the signal/waveform. (This may be the reason headphones are enjoyed by many.)  Once it leaves the speaker, this waveform, the original signal, makes a beeline to our ears but it also travels to every corner of our room, where it is reflected and after a while, makes it to our ears as well. If these waveform reflections that are relatively loud hit our ears within the window during which we cannot distinguish their arrival time from the incoming original waveform, they become the noise that competes with the original signal/waveform and consequently lowers the signal to noise ratio. Reducing these competing waveforms in number or amplitude through absorption or diffusion will increase your SNR. You do want to retain some reflections for a sense of space and ambiance so pure absorption is not indicated. You just want fewer or softer competing waveforms (noise) so the original waveform (signal) predominates. Before I had my dedicated room, I would rearrange the living room furniture when my wife was away and place freestanding 2x4 acoustic absorbers at the first reflection points for extended listening sessions. This simple addition made a huge difference and made me a believer.

As related examples in an  acoustic vein, speaker isolation footers/stands and stiff cabinetry enhance SNR by ensuring the acoustic waveform from the driver is created only by the electrical signal and not by physical vibrations rattling the driver and creating extraneous and competing waveforms. Phono cartridges, platters and tonearms are isolated to avoid extraneous influences that would change the way the stylus is able to faithfully retrieve and transmit only the information from the signal embedded in the groove. If you think something is interfering with any of your waveforms/signals before they reach your ears, fix it if you can. Any wave, anywhere. Source, electronics, speakers and perhaps most significantly, your listening room. You have paid good money and paid close attention to the SNR up to the point the signal leaves your speaker.  Why stop there?

Occam’s Razor: The simplest explanation for why a change in your system sounds better is because you improved the SNR somewhere along the chain (you kept your waveform as close to the original as possible).

 

 

 

All timbre information is contained within the original waveform.

From Britannica.com: "timbre, quality of auditory sensations produced by the tone of a sound wave."  

From DSP Guide.com: "The perception of a continuous sound, such as a note from a musical instrument, is often divided into three parts: loudness, pitch, and timbre (pronounced "timber").  Loudness is a measure of sound wave intensity, as previously described.  Pitch is the frequency of the fundamental component in the sound, that is, the frequency with which the waveform repeats itself. While there are subtle effects in both these perceptions, they are a straightforward match with easily characterized physical quantities.Timbre is more complicated, being determined by the harmonic content of the signal." 

"Harmonic content of the signal."  I don't know where harmonic content would reside other than in the waveform.

Again, it's all about the waveform and its purity. Psychoacoustics doesn't start until the waveforms have hit your eardrum. By then, damage done.

The title of your link is “Perceptual attributes of acoustic waves – Timbre”. I believe you make my point right there but I will expand further.

 

You cite the following factors:

1. signal time variance (envelope) 
2. degree of attack and decay synchrony of the sine components;
3. presence or absence of high-frequency inharmonic energy in the attack portion of a signal;
4. spectral energy distribution (frequency, amplitude and phase values of the sine components of a complex signal - may change with changes in intensity and register, even for a given instrument); and 
5. spectral energy distribution time-variance (spectral flux or "jitter").

Where in the article does it refer to something other than a waveform?

a. The “signal” is a waveform

b. “Sine components” are only found in a wave

c. “inharmonic energy” refers to waves

d. “Frequency amplitude and phase changes of the sine components” refer to waves

e.  and from the article itself: “Helmholtz was the first scholar to link timbre (a perceptual aspect of sound waves) to spectral distribution (a physical aspect of sound waves). He specifically focused on the spectral distribution of the steady state portion of sound signals (defined below). This approach overlooked several acoustical aspects of sound signals, such as attack (onset transients) and signal/spectral time variance, both of which have been proven important to timbre perception.” 

Where do you think onset transients or signal/spectral time variances are found, if not during the delivery of waves? These are not created in one’s head. 

 

Regarding crosstalk, it is defined by Wikipedia as “usually caused by undesired capacitive, inductive, or conductive coupling from one circuit or channel to another.”

Meaning that the electromagnetic waves created in one wire impact the electromagnetic waves in an adjacent wire, thereby making it different from the original signal. Crosstalk is an example of electromagnetic interference.  Waves again.

 

Referring to psychoacoustics, Ansys.com states: “Psychoacoustics is the study of how humans perceive sound. It’s a relatively young field that began in the late 1800s to help aid in the development of communications. Psychoacoustics combines the physiology of sound — how our bodies receive sound — with the psychology of sound, or how our brains interpret sound.”

 

Our stereo systems can only address what sounds (waveforms/signals) our body receives. As I said earlier, once it hits the brain, the damage is done. Your brain cannot repair what was missing from or added to the original signal. It can interpret it, but it cannot change it.  That has to happen before it gets to the eardrum.

 

You finish with: “No audio system is perfect high fidelity reproduction ... They all translate in a relative way some experience, timbre and spatial acoustic qualities, which are not reducible at all to signal noise ratio on a line”.

 

First of all, they are reducible, but only in part. The other influence is the speaker’s interaction with the room and that is why I continue to emphasize that to get the best signal/waveform to your ears, you need to address the signal in the room as well as in your electronics. What happens to the signals in your head is your problem and yours alone.

 

 

 

 

 

 

 

My apologies for how I ended the previous post and how it might appear.  I should have said "the signals in your head are your business and yours alone". 

Talking about imperfections, I have to admit I am an example. I had stated above that distortion contributes to the SNR but according to those who actually work in the field, I am mistaken. Distortion, although perhaps noisy, is not considered to contribute to the signal to noise ratio, although there are those who incorporate into a SINAD (signal-to- noise-and-distortion ratio). All this being said, the main thrust of my post was to encourage folks to pad their cells. Apologies if I misled some in my quest to accomplish that.