"What HiFi" - can it be trusted?
 

On Sun, 18 Jan 2004 20:58:07 -0000
"Wally" wrote:

I just used a tone generator to play a 400Hz and a 450Hz tone together, and
there was no 50Hz tone that I could hear. How's that?

Try 400 and 401 Hz then - far more obvious.

--
Spyros lair: http://www.mnementh.co.uk/ |||| Maintainer: arm26 linux

Do not meddle in the affairs of Dragons, for you are tasty and good with ketchup.

"What HiFi" - can it be trusted?
 

On Sun, 18 Jan 2004 22:36:52 +0000, Chris Isbell
wrote:

Simple addition of two frequencies does NOT result in any new
frequencies. Only non-linearities causing one of the signals to be
multiplied by the other (aka 'mixing', 'modulating' or 'heterodyning')
will cause sum and difference frequencies to be created.

That poses the question, how can I tune instruments accurately using
beat frequencies?

If you want them to be "perfectly" (and I use that term precisely) in
tune, you tune for zero beats. This is quite easy for unisons and
octaves, takes a bit of practice for 5ths and 4ths.

In the real world, we usually tune perfect octaves, but tempered
(changed) other intervals. A piano tuner learns to tune 5ths a
certain number of beats flat, major 3rds a certain number of beats
sharp. Then there's "stretch tuning", where the top end is tuned
increasingly sharp, the bottom end increasingly flat. On an upright
piano, this is done to a greater or lesser extent depending on whether
the instrument is close against a wall or not.

Sorry you asked? :-)

"What HiFi" - can it be trusted?
 

On Sun, 18 Jan 2004 16:19:08 +0000, Ian Molton wrote:

On Sun, 18 Jan 2004 16:09:15 +0000 (UTC)
(Stewart Pinkerton) wrote:

Im wondering if this is the same 'problem' as hearing a 50 Hz tone when
you play a 400 and 450 Hz tone ;-)

That doesn't happen in linear systems, and I thought that linearity
was your big thing? :-)

Oh god not again.

You HEAER it. it doesnt actually exist.

What, voices in your head? Or intermodulation products which don't
occur in linear systems?
--

Stewart Pinkerton | Music is Art - Audio is Engineering

"What HiFi" - can it be trusted?
 

On Sun, 18 Jan 2004 19:10:23 +0000, Kurt Hamster
wrote:

On Sun, 18 Jan 2004 18:06:56 +0000, Chris Morriss used
to say...

In message , Kurt Hamster
writes
On Sun, 18 Jan 2004 16:19:08 +0000, Ian Molton used
to say...

On Sun, 18 Jan 2004 16:09:15 +0000 (UTC)
(Stewart Pinkerton) wrote:

Im wondering if this is the same 'problem' as hearing a 50 Hz tone when
you play a 400 and 450 Hz tone ;-)

That doesn't happen in linear systems, and I thought that linearity
was your big thing? :-)

Oh god not again.

You HEAER it. it doesnt actually exist.

Don't tell me you believe in ghosts too?



You only hear it if either your system is non-linear, and therefore
multiplicative mixing is taking place, or that you are listening at such
a high level that your ears are being driven into overload.

If you can hear it then it exists. One cannot hear what doesn't exist.

One certainly can, and it would appear that people around here often
do!
--

Stewart Pinkerton | Music is Art - Audio is Engineering

"What HiFi" - can it be trusted?
 

On Sun, 18 Jan 2004 23:05:03 +0000, Ian Molton wrote:

On Sun, 18 Jan 2004 20:58:07 -0000
"Wally" wrote:

I just used a tone generator to play a 400Hz and a 450Hz tone together, and
there was no 50Hz tone that I could hear. How's that?

Try 400 and 401 Hz then - far more obvious.

Um, you think that he can hear a 1Hz tone more easily than a 50Hz
tone? From which planet are you connected to the Internet?
--

Stewart Pinkerton | Music is Art - Audio is Engineering

"What HiFi" - can it be trusted?
 

On Sun, 18 Jan 2004 18:05:14 +0000, Julian Fowler
wrote:

On Sat, 17 Jan 2004 11:51:36 +0000 (UTC),
(Stewart Pinkerton) wrote:


You can get at least 200 CDs onto a 120GB hard disk if you insist on
computer storage, and I don't know *anyone* who listens to more than
200 different discs in an average year.

RAOTFL ...

A quick estimate suggests that I probably listen to something like
2000 different discs in an average year.

I hope you get paid for that................
--

Stewart Pinkerton | Music is Art - Audio is Engineering

"What HiFi" - can it be trusted?
 

On Mon, 19 Jan 2004 00:11:36 +0000
Laurence Payne wrote:

That poses the question, how can I tune instruments accurately using
beat frequencies?

If you want them to be "perfectly" (and I use that term precisely) in
tune, you tune for zero beats.

this rather suggests the effect is audible, nontheless ;-)

--
Spyros lair: http://www.mnementh.co.uk/ |||| Maintainer: arm26 linux

Do not meddle in the affairs of Dragons, for you are tasty and good with ketchup.

"What HiFi" - can it be trusted?
 

On Mon, 19 Jan 2004 08:05:13 +0000 (UTC)
(Stewart Pinkerton) wrote:

Um, you think that he can hear a 1Hz tone more easily than a 50Hz
tone? From which planet are you connected to the Internet?

a 1 Hz beat frequency? you bet.

--
Spyros lair: http://www.mnementh.co.uk/ |||| Maintainer: arm26 linux

Do not meddle in the affairs of Dragons, for you are tasty and good with ketchup.

"What HiFi" - can it be trusted?
 

In article , Chris Morriss
wrote:


Simple addition of two frequencies does NOT result in any new
frequencies. Only non-linearities causing one of the signals to be
multiplied by the other (aka 'mixing', 'modulating' or 'heterodyning')
will cause sum and difference frequencies to be created.

That is correct. However I suspect that people may be talking at
cross-purposes in this thread as there is a distinction between equipment
non-linearities and ones within the hearing/perception mechanism. One
alters the soundwave reaching the head, the other does not. Hence one is
'real' in a different way to the other.

I've no idea over what amplitude range the ears are linear, but if the
ear is presented with sounds that drive it into non-linearity then the
sum/difference frequencies will be heard I guess.

Anyone know how linear the sound detection mechanism of the ear is?
(Genuine question, 'cause I don't know)

According to current understanding/research, human hearing is inherently
non-linear at *all* levels above the threshold of perception. All my papers
on this are at the office, however I collected these and looked at the
topic a year or two ago when a related topic came up. IIRC the amplitude of
the response of the hair cells in the ears has been measured to only
increase with the *cube root* of the magnitude of the incident sound. This
helps explain a number of curious perception effects, and also how hearing
copes with a huge dynamic range.

One effect is various forms of 'intermodulation distortion' which occur in
the physical sensing mechanisms of the ear even at low levels.

IIRC builders of pipe organs have sometimes exploited this to use pairs of
low-frequency pipes to simulate a lower-frequency pipe and get very low
percieved notes when they do not have the actual space or money for the
larger pipes this would require.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

"What HiFi" - can it be trusted?
 

On Sun, 18 Jan 2004 23:05:03 +0000, Ian Molton wrote:

On Sun, 18 Jan 2004 20:58:07 -0000
"Wally" wrote:

I just used a tone generator to play a 400Hz and a 450Hz tone together, and
there was no 50Hz tone that I could hear. How's that?

Try 400 and 401 Hz then - far more obvious.

You do not hear a tone at 1Hz in these circumstances - you hear beats.
These are very different. There is no tone, there is no need for any
non-linearity that might generate a tone. You are simply hearing
pressure peaks moving in and out of phase.

d

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