Occam's Razor: The Signal to Noise Ratio


Occam's Razor can be paraphrased as "the best explanation is the simplest one". In the case of audio, I suggest the best "explanation" for the best sound is the highest signal to noise ratio. We commonly pursue this with equipment topology, vibration isolation for turntables, electronics and speakers, electrical isolation with dedicated circuits, component isolation, cable hygiene and all our other efforts to eliminate noise pollution. I believe it extends well beyond this, culminating not in what comes out of the speaker, where I think many folks stop, but rather what finally hits our ears. This means wave interference in the listening room is one of our largest noise contributors.

 

I have been fortunate in having the time and means to curate a nice system, but I recognized that it would never deliver the best SNR if the signal that leaves the speaker is corrupted by the noise created as it careens throughout the room before it reaches my ear. Over the last few months, I have added room treatments that together cost more than any one single component in my system.  I initially paid attention to first reflections, creating what I call the “circle of silence” with absorption on the walls, ceiling and floor. I also directed my efforts towards speaker boundary interference response with appropriate placement of the speakers and listening position. Bass traps and a distributed bass array deal with uneven lower bass response. Not wanting to dull the room with overabsorption, I added pure diffusion or a combination of diffusion and absorption.

 

What I now have is a system that not only provides a very accurate signal, but one that is not muddied by all of the other signals (noise) bouncing off the room surfaces.  Instruments and voices are clear with an obvious start and stop. While the system always had decent width and height, they are greater now.  The most significant contribution is that the soundstage now extends in front of and far behind the speakers. On a good rock recording, I can place the drum set, the bass, the keyboard, the vocalists and the guitars three-dimensionally. Classical and jazz are even more remarkable. It is stunning and at times, even startling.

 

I recognize that not everyone has a room they can devote to their audio pursuits, but within your means and what you and yours find socially acceptable, you should do everything you can to attend to the noise your room adds to your pure and pristine signal. Fuses, power cords, cables, amplifier design, speaker type, etc., all pale in comparison. No matter how your particular equipment tastes run, if you were to put your system in my room, it would likely sound better.

 

Bottom line, defend and protect your hard won signal from all the noise throughout the entire reproduction process. Everything counts, especially the room.

 

tcutter
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The SNR is a perceived signal value over a noise background, being measured or directly perceived by the ears... It is defined in decibels the signal being posed as higher in decibel over the noisy background.....

Then the SNR is inherent to any piece of gear extend to and integrate the house electrical grid which had a noise floor of his own and not only apply to the system pieces ... For sure the room acoustic and the electrical grid of the house and even the vibrations of the gear and the uncontrolled  resonance of the speakers   will greatly impact the signal perception... Way more than even the choice between two good amplifier with a similar SNR or slightly different SNR as 2 high-end  amplifiers for example, or two low cost one with similar measured SNR ..

 

 

 

I must say that you can apply Occam razor in scientific experiments...Because scientific experiments are created to isolate a factor or a cause to confirm or infirm a theory ... Then the simple explanation which emerge is the factor and cause which is isolated in an experiment designed by a set of measured controls to do it specifically...

You cannot apply it in the same directed way in audio experience which is not a singular experiment , but a perceived experience resulting from hundred of factors combined...These factors cannot often be eliminated to improve our experience, they generally must be optimally adressed and put under control one by one and together ...

And in audio many factors are not directly related to the SNR as a measured factor of the gear itself but are indirectly contributing to the perceived experience in a huge way... As the electrical grid noise floor of the house, the inner ears measures, the HRTF ( head measures transfer related function ) the acoustic content of the room , his geometry and topology , the vibration-Resonance of the gear, the disturbing effect of crosstalk in any stereo system  etc...

I like room treatments, Occam's Razor, and the Occam processors, but I think the SNR metaphor is not quite right.

If that were true a purely absorptive room would be the right approach, but in fact it is not.  As you've found, a combination of diffusion and absorption is the right approach, so I think cooking might be a better metaphor.

You don't want a pure sound, because speakers are not meant to go into sterile environments, you want an enveloping sound that makes you feel passionate about the illusion you end up perceiving.  And, passionate as I may be about room acoustics and measurements, recognize that they are tools to reach a satisfying emotional experience.

Not to anyone in particular - the signal to noise ratio on internet forums dwarfs every other example in difficulty. Would that it were that diffusion and absorption could buffer human discussions. Alas, there are times when only "mute" does the trick.

@bolong- 

                                                  LOL

you got it backwards, simplest comes first. i.e. the simplest explanation is most often correct.

The origin and purpose are mostly unknown to us, I went to wiki:

" William of Ockham himself seems to restrict the operation of this principle in matters pertaining to miracles and God’s power, considering a plurality of miracles possible in the Eucharist[further explanation needed] simply because it pleases God.[12]"

Thus, better S/N ratio must please God.

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).

 

 

 

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A timbre experience is a subjective perception which come from a multidimensional set of interacting parameters and cannot be reduced to SNR concept and to a physical waveform...

Audio is not so much about the gear but about psychoacoustics...

Occam razor is a philosophical concept not an acoustical concept...It is a general methodological concept that cannot be used to justify the reduction of a complex concept and experience as "timbre" to be just a SNR simply measured factor..
 
In fact the definition of timbre in acoustics EXCLUDE a simple SNR definition based only on the physical waveform spectral distributions ...
 
«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.»
 
 
«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.»
 
Then the problem with your description is if the recorded acoustics parameters picked by the sound engineer in this album you listen to can be reduced to SNR total sum of the gear system by contrast the experience you will have from it in your room with your ears/brain specific characteristics cannot be reduced to a SNR . Timbre is a subjective very complex experiencve which cannot be understood and controlled with the SNR concept. Our ears/brain /room condition create the sound experience, they do not convey it in a passive way as a cable or even an amplifier will do adding only some noise level to the signal. Then you description is not even wrong , it is a simplistic reductive reduction of a complex acoustic phenomenon to a set of linear signals on a channel. But the ears/brain dont work linearly in the linear Fourier time domain. Then the SNR concept capture only a part of the audio problem, not the acoustic more important part . All these metaphors Using the SNR concept are not enough to understand timbre experience in a room ... the simplest metaphor are not always the good one , Occam razor or not.... Then you are not even wrong in your description reducing all audio aspects to SNR ...
 
The reason for such metaphors with SNR is the audiophile focus on gear design more than on acoustics itself...
 
 

 

 

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.

All timbre information is contained within the original waveform.

You forgot to observe the way our ears-brain-room will modify a recorded timbre and will transform it in an experienced timbre in a specific way for each different room and ears/brain.

Timbre is not reducible to a SNR analysis...

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."

Instead of these too simplistic definition read the article i suggested on psychoacoustics

http://acousticslab.org/psychoacoustics/PMFiles/Module06.htm

Timbre is not only determined by the harmonic content of the waveforms but by his time envelope and timing dimensions of the room also by the dynamic of the sound...

  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").

 

Your sentence here resume all your misunderstanding:

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.

For sure you are right ...But the physical waveform in the room is an acoustic translation of the recorded waveform not a mere deformation or a perturbation or a mere loss from a so called pure signal but an acoustic positive-negative trade-off transformation which cannot be explained by only a SNR metaphor... For example crosstalk effect result in a loss of spatial information in all stereo system and had no direct relation to only measured SNR of the gear but resulted from physical stereo disposition and physiological conditions.

Then you are not wrong you forgot half of the story... Timbre is experienced in a room and with some ears... Then it is not only about electronic reproduction it is about acoustic translation ...Then it is more than just SNR meassures...

Psychoacoustics begins before the waveform has hit your eardrums. 😁It begins in the design of the gear itself , for example in the Dr. Choueiri design of his filters to erase the effect of crosstalk . This is way more than SNR physical measures, it is psychoacoustics design .

Psychoacoustics is the root and the canopy of the audio tree...Gear design resulted from this science at the end. It is way more than just SNR measures...Your are not even wrong and this is my point... I added only the part of the acoustic story you inconsciously  put under the SNR rug metaphor...

Audiophile experience is more than buying gear design with good measured SNR, it is also acoustics and psychoacoustics varying parameters in the TRANSLATION of acoustic recorded waveform for your room/ears/brain in another perceived experience which will differ from the recorded waveform by acoustic definition..

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

 

 

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 capacitiveinductive, 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". 

Perlman On Heifetz

Here's my example of SNR - Heifetz freewheelin' it. I remember Perlman also saying upon Heifetz's death that he  played like "lava."

Heifetz Plays Sibelius

 

Heifetz is so above most musicians, than someday i remember listening to him in a quintet of Schubert and it will not be my reference version even if i liked it for sure because Heifetz perfect sound control put him unvolontarily in the front seat... It was more a concerto with a soloist than a quintet... It was not his fault his mastery and perfection sound exceed most... I was hearing a concerto for Heifetz not so much Schubert quintet ... 😊

it was thirty years ago and i cannot forget it so astounding and surprizing it was for me ...

Sometimes a musician touch something near perfection ...But it can be detrimental in a way when playing with the others who are more casual ordinary mortals...😁

He represent perhaps more than everyone absolute mastery of violin ...it is not even debatable or about taste... Ask any violinist...

My favorite violin works is Szeryng Bach sonata first version ....But the Sibelius with Haifetz match it for sure ... No one beat Heifetz...But here in Bach Szering is beside him or not far... Nobody ever beat this Bach interpretation anyway in power of expression for me  ... None...Even the Heifetz god...Music is than more than SNR or perfection , it is also  some  controlled "imperfection" called "expression" ...

 

 

Indeed you are right.

I was actually making a little funny with this topic. Artists like Heifetz and Artur Rubenstein sometimes caught grief for twiddling a bit with the notes by subtly re-writing and spontaneously improvising and embellishing what was "on the page." Rubenstein would take improvisational liberties with Chopin sonatas and was accused of creating "noise." So, their signal-to-noise ration could be said to have triumphed noise over signal even though this is not quite analogous to the discussion about electronics.

Exactly 

...

Expression is not less hard to reach than perfection...

As said the genius french poet René Char :

«Imperfection is the peak»😊

Yeah, it's the hardest lesson for humans to learn - perfection is not the absolute and imperfection can be your best friend.

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.

And I just did "pad the cell" to kill off some room nodes - finally. Worth it in ways I am still listening to to see just what exactly is taking place.