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Sine and square waves percieved pitch, why?
Sine and square waves percieved pitch, why?
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Old 5th March 2005, 11:02 AM   #1
baggystevo82 is offline baggystevo82  United Kingdom
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Default Sine and square waves percieved pitch, why?

Hello,
I have this question as part of my digital audio module coursework, and would very much appreciate some help! heres the question:
Quote:
d) Quite difficult: you will need to do this with a neighbouring group. Tune one sig-gen to a frequency close to the lower end of your hearing range, giving sine waves. Use the other sig-gen to give square waves and alter the frequency so that you can hear within that sound a sound which is the same as the first sig-gen is giving. What is the frequency on the meter of the second sig-gen? What is the ratio of the two frequencies? Tune both sig-gens to higher frequencies and see if you can repeat the test. What is the ratio of the two new frequencies? Do you have an explanation?
and here's the graph of my results. It seems a bit strange that there's a sudden changeover in characteristics of the graphs and I'm confused....help....
Cheers,
Steve
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Old 5th March 2005, 12:39 PM   #2
jan.didden is offline jan.didden  Europe
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Well,

From the way that the question was framed, it looks like you should EXPECT something irregular, so your curve may be quite alright. As for an explanation, I don't have one, but I would google things like pitch perception or pitch shift with frequency.

Jan Didden
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Old 5th March 2005, 12:47 PM   #3
baggystevo82 is offline baggystevo82  United Kingdom
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Hi,
Cheers, yeh that's what I thought. I think my lecturer just wanted us to do a very low frequency, and one high one, but I got curious and homed in on the area around which the change occurs. It's just the almost instant change that surprised me, within 1/4 of a Hz or so, seems like there's some strange phenomenon I don't know of, besides harmonics of square waves etc that's causing it....hmmmmm.....ponder ponder....
Thanks,
Steve
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Old 5th March 2005, 12:59 PM   #4
jan.didden is offline jan.didden  Europe
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Yes, the sharpness of the change IS funny, mother nature seldom builds something like that. Hmmm....

Jan Didden
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Old 5th March 2005, 04:33 PM   #5
KBK is offline KBK  Canada
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The human ear works as a 'diode' and only hears the leading edge of a given note. perhaps, if you played withthe DUTY CYCLE of the given sqare waves, the percieved answer may alter itself in some manner, compared to the original observations.

Also, the ear is timing and transient sensitive, which should be a logical extrapolation (follow the logic trail) of the statement that the ear works as a diode. This means, harmonics, timing (time related components surrounding the transient information) and amplitiue of the transient components are critical for human Observation.

If the 10% and the 90% points of the square wave (as normally considered) are cleaned up, via a small dose of inductance, the answer may pop out in a more clear fashion.

The fact that the human ear is capable of resolving transient information down to less than 100,000th of a second (timing issues, not frequency) is interesting. This is due to the timing of arrival of signals between each ear for spatial recognition of information, at the very least, and is a known human skill and phenomena,

This means, clocking of digital systems and the like, due to nyquist, must exceend 225khz sampling in extreme accuracy, to meet the minimum requirement for exceeding human resolving capacites, as recognized ---at this time---. Who knows, that figure may have to be revises YET AGAIN....and again..as it has been over the years.

I suspect you are hearing simple negative or postive edges of the given waveform, and the brain 'mixes up' the leading edge, depending on the phase transition at a given frequency. This may be why a low frequency was specified, so the area of frequential overlap between the two frequencies is as large as possible.

What I mean, is the time factors involved as an issue, at the transition point for both the square and sine are enlarged, at the lower frequencies,and the phenomena may be easier to resolve, or confuse the mind-brain, at the lower frequency. Simple signal ear-brain phasing issues. We recognise the transient, not the phase of it. Low frequencies create negative and positive rarefraction-compression of the air, regardless of the frequency of the signal, that can be easily recognised, even with the pahse being reversed. Otherwise, signals would be more garbled when they are, when they are wired out of pahse with regard to your speakers and speaker systems.

Some people, like me, due to exposure in the world of design on a very regular basis, have taught ourselves to recognise these issues and resolve (with listening, and completing large numbers of 'single cause analysis' experiments) them to a very high level, simply due to a larger understanding of what I am hearing when I listen to audio signals, in any fashion. Many experiments, many correlations, etc. It puts me one step ahead of the next guy who is designing audio gear.
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Old 5th March 2005, 05:13 PM   #6
jan.didden is offline jan.didden  Europe
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Man, you should get published in some scientific journal, this is sensational! Your insight and knowledge is what we all have been waiting for. The ear as diode, wow, who would have thought that??

Jan Didden
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Old 5th March 2005, 05:21 PM   #7
baggystevo82 is offline baggystevo82  United Kingdom
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Cheers for that! It was kinda what I was thinking I think, Ill have to have a good think about that one.
Cheers,
Steve
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Old 5th March 2005, 05:47 PM   #8
KBK is offline KBK  Canada
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The ear, 'as a diode' has been known for quite some time. The human voice is single-sided, as in the fact that the entire human voice is a positve pressure front, with transient timing and amplitude as the founding components of intelligibility. Same thing behind the human behaviour of 'clapping' of hands.

Our hearing has evolved around these considerations.

Note that horn speakers would not work if this were not true, as they make the negative component of the waveform resemble total garbage, if it is measured.

There is incredibly high distortion the negative components of a horn speakers's acoustical signal, yet most percieve horn signals as beng more intelligible.

There is nothing new in these statements. It is all old and well covered work. Possibly not well considered, or well connected, but the parts of the solution and answers are all well known.

All these things follow through to being essential understandings in the art of electronics design. First you must understand how people hear things. Then you can design electronics. Forget about measuring anything, or designing and building it. These considerations are the most major points of consideration, and belong at the top of "page one, chapter one", of designing audio gear, of any kind. Whatever the case may be.

And just about no-one in the entire industy undertands these things, it seems. For example, electronic feedback networks introduce phase or time skewed transient components, so they inherently sound like **** to the human ear. This is simple extrapolation of the above related facts.

Yet....no-one seems to 'get it'.

So I'll do exactly what I usually do. I'll say it quietly, and nicely in some small backwater or corner like this one here...and sooner or later, people will pick it up, and it will enter the lexicon of design in the realm of logical analysis in electronics design. Heck, you might end up seeing such information as part of an article in Stereophile 2-3 years from now or something similar to that. And, no-one seems to know where such information comes from, or where it originated. Some guy will be applauded and complemented on his work, how smart he is, etc, and it won't be me. I suspect the JAES magazine has had similar articles, but not all the perinent info in one spot, at one time, so people can connect the dots. For once. (involving this particular application of logic concerning this exact subject) Please and thank you......

This is one of my favorite games, and I've played it dozens of times. Seeding. Who cares, really, as long as they eventually figure it out.
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Old 5th March 2005, 06:33 PM   #9
MBK is offline MBK  Singapore
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KBK,

almost namesake

Love your seeding approach - I often have the same kind of thoughts. Not that I necessarily have much to seed, in DIY audio at least. Reminds me of Jorge Luis Borges' publication of single very short book concepts - he didn't feel like actually writing the book As a special pun to Pass one could mention the title of one of Borges' books - The Aleph.

Anyway , I once started a dicussion with relevant info here, the single ended nature of things .

About the ear, not only does it appear to work as a single ended detection device with highest sensitivity at the zero crossing, it also has active, highly nonlinear amplification mechanisms. This was first suspected in the 60's, then disregarded for decades, and recently well demonstrated. See here for example:

Inner Ear Amplifiers . Poor Gerbils.

All this explains the apparent insensitivity to high levels of certain distortion, such as low harmonics distortion, and high sensitivity to other forms of distortion, such as crossover distortion, or high order distortion components.

Many other references exist ... somewhere...
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Old 5th March 2005, 07:23 PM   #10
baggystevo82 is offline baggystevo82  United Kingdom
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All brilliant stuff! If you're trying to influence me for the future its working, hehe.
Thanks again!
Steve
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