Help with understanding pink noise results
 

Good morning experts ;-)

I've been going through my HFN test record. Most of it makes sense but I
don't understand my pink noise results. They show an approximate 10 dB /
decade tilt, which is what I would expect from pink noise. For example,
here's a frequency analysis of a 'perfect' pink noise sample generated
by Audacity.

http://www.nu-ware.com/Misc/Screensh...nk%20Noise.png

Here is the result of the HFN pink noise test using my M55E cartridge.

http://www.nu-ware.com/Misc/Screensh...nk%20Noise.png

However, when I look at test results around the web I see essentially
flat curves from pink noise tests. Like this:

http://www.tnt-audio.com/sorgenti/shure_m97xe_e.html

So, what am I missing?

Help with understanding pink noise results
 

On Wed, 11 Mar 2015 10:39:25 +0000, Sumatriptan
wrote:

Good morning experts ;-)

I've been going through my HFN test record. Most of it makes sense but I
don't understand my pink noise results. They show an approximate 10 dB /
decade tilt, which is what I would expect from pink noise. For example,
here's a frequency analysis of a 'perfect' pink noise sample generated
by Audacity.

http://www.nu-ware.com/Misc/Screensh...nk%20Noise.png

Here is the result of the HFN pink noise test using my M55E cartridge.

http://www.nu-ware.com/Misc/Screensh...nk%20Noise.png

However, when I look at test results around the web I see essentially
flat curves from pink noise tests. Like this:

http://www.tnt-audio.com/sorgenti/shure_m97xe_e.html

So, what am I missing?



Those last curves have been "corrected" to look flat. Essentially what
they are showing is the difference between the perfect pink noise and
that recovered from the record.

Yours is showing signs of being a bit saggy at the top and bottom of
the band. Could do particularly with a touch of bass lift.

d

Help with understanding pink noise results
 

Sumatriptan wrote:


I've been going through my HFN test record. Most of it makes sense but I
don't understand my pink noise results. They show an approximate 10 dB /
decade tilt, which is what I would expect from pink noise. For example,
here's a frequency analysis of a 'perfect' pink noise sample generated
by Audacity.

http://www.nu-ware.com/Misc/Screensh...nk%20Noise.png

Here is the result of the HFN pink noise test using my M55E cartridge.

http://www.nu-ware.com/Misc/Screensh...nk%20Noise.png

However, when I look at test results around the web I see essentially
flat curves from pink noise tests. Like this:

http://www.tnt-audio.com/sorgenti/shure_m97xe_e.html

So, what am I missing?


** Pink noise has equal amounts of energy in each octave or fraction thereof.

Spectrum analysis software ( like FFT ) has to be set to read the signal in terms of octaves rather than some fixed bandwidth in Hz in order to see a horizontal graph.


.... Phil

Help with understanding pink noise results
 

In article ,
Sumatriptan wrote:
Good morning experts ;-)

I've been going through my HFN test record. Most of it makes sense but I
don't understand my pink noise results. They show an approximate 10 dB /
decade tilt, which is what I would expect from pink noise. For example,
here's a frequency analysis of a 'perfect' pink noise sample generated
by Audacity.

http://www.nu-ware.com/Misc/Screensh...nk%20Noise.png

Here is the result of the HFN pink noise test using my M55E cartridge.

http://www.nu-ware.com/Misc/Screensh...nk%20Noise.png

However, when I look at test results around the web I see essentially
flat curves from pink noise tests. Like this:

http://www.tnt-audio.com/sorgenti/shure_m97xe_e.html

So, what am I missing?

I'd say it's likely impossible to record perfect pink noise to vinyl.

The peaks you're seeing above 10kHz are likely down to the capacitance of
the connecting leads. If you try a different type, you'll likely see a
different result. Not quite sure of the theory behind this, but it's what
I've experienced with variable reluctance cartridges. Perhaps an expert
would explain it?

--
*It's o.k. to laugh during sexŒ.Œ.just don't point!

Dave Plowman London SW
To e-mail, change noise into sound.

Help with understanding pink noise results
 

On Wed, 11 Mar 2015 11:21:54 +0000 (GMT), "Dave Plowman (News)"
wrote:

In article ,
Sumatriptan wrote:
Good morning experts ;-)

I've been going through my HFN test record. Most of it makes sense but I
don't understand my pink noise results. They show an approximate 10 dB /
decade tilt, which is what I would expect from pink noise. For example,
here's a frequency analysis of a 'perfect' pink noise sample generated
by Audacity.

http://www.nu-ware.com/Misc/Screensh...nk%20Noise.png

Here is the result of the HFN pink noise test using my M55E cartridge.

http://www.nu-ware.com/Misc/Screensh...nk%20Noise.png

However, when I look at test results around the web I see essentially
flat curves from pink noise tests. Like this:

http://www.tnt-audio.com/sorgenti/shure_m97xe_e.html

So, what am I missing?

I'd say it's likely impossible to record perfect pink noise to vinyl.

The peaks you're seeing above 10kHz are likely down to the capacitance of
the connecting leads. If you try a different type, you'll likely see a
different result. Not quite sure of the theory behind this, but it's what
I've experienced with variable reluctance cartridges. Perhaps an expert
would explain it?

Hadn't thought about the vinyl limitations. The bottom end rolloff
probably happened during mastering to stop the cutter ripping the
vinyl in two.

The top end is certainly some sort of resonance - whether mechanical
in the cartridge, or as you say electrical between the cartridge
inductance and the cable capacitance.

d

Help with understanding pink noise results
 

On Wed, 11 Mar 2015 11:39:29 GMT, (Don Pearce) wrote:

On Wed, 11 Mar 2015 11:21:54 +0000 (GMT), "Dave Plowman (News)"
wrote:

In article ,
Sumatriptan wrote:
Good morning experts ;-)

I've been going through my HFN test record. Most of it makes sense but I
don't understand my pink noise results. They show an approximate 10 dB /
decade tilt, which is what I would expect from pink noise. For example,
here's a frequency analysis of a 'perfect' pink noise sample generated
by Audacity.

http://www.nu-ware.com/Misc/Screensh...nk%20Noise.png

Here is the result of the HFN pink noise test using my M55E cartridge.

http://www.nu-ware.com/Misc/Screensh...nk%20Noise.png

However, when I look at test results around the web I see essentially
flat curves from pink noise tests. Like this:

http://www.tnt-audio.com/sorgenti/shure_m97xe_e.html

So, what am I missing?

I'd say it's likely impossible to record perfect pink noise to vinyl.

The peaks you're seeing above 10kHz are likely down to the capacitance of
the connecting leads. If you try a different type, you'll likely see a
different result. Not quite sure of the theory behind this, but it's what
I've experienced with variable reluctance cartridges. Perhaps an expert
would explain it?

Hadn't thought about the vinyl limitations. The bottom end rolloff
probably happened during mastering to stop the cutter ripping the
vinyl in two.

The top end is certainly some sort of resonance - whether mechanical
in the cartridge, or as you say electrical between the cartridge
inductance and the cable capacitance.

d

In fact I've just remembered I did have a look at how a V15 cart
responded to cable capacitance. It's he

http://www.soundthoughts.co.uk/read/cartridge.pdf

It assumes the cartridge to be nominally flat with no capacitive
loading. The peak is at about 10kHz.

d

Help with understanding pink noise results
 

In article , Dave Plowman (News)
wrote:
In article , Sumatriptan
wrote:
Good morning experts ;-)

I've been going through my HFN test record. Most of it makes sense but
I don't understand my pink noise results. They show an approximate 10
dB / decade tilt, which is what I would expect from pink noise. For
example, here's a frequency analysis of a 'perfect' pink noise sample
generated by Audacity.

http://www.nu-ware.com/Misc/Screensh...nk%20Noise.png

Here is the result of the HFN pink noise test using my M55E cartridge.

http://www.nu-ware.com/Misc/Screensh...nk%20Noise.png

However, when I look at test results around the web I see essentially
flat curves from pink noise tests. Like this:

http://www.tnt-audio.com/sorgenti/shure_m97xe_e.html

So, what am I missing?

I'd say it's likely impossible to record perfect pink noise to vinyl.

FWIW I checked the 'pink' and 'white' noise bands on a variety of test LPs.
They were all wildly different in ways that didn't simply mimic the
response of the cartridge I was using.

The best way I found to do measurements of frequency response was to use a
stepped or swept tone test band from a test disc.

http://www.audiomisc.co.uk/HFN/LP4/NewLampsForOld.html

shows some examples using the Analog Productions test LP.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Help with understanding pink noise results
 

In article ,
Jim Lesurf wrote:
FWIW I checked the 'pink' and 'white' noise bands on a variety of test
LPs. They were all wildly different in ways that didn't simply mimic the
response of the cartridge I was using.

I have a digital equaliser which generates what it claims to be pink noise
- and uses that to auto-eq a speaker system. It's very different from the
pink noise Audacity generates.

My feeling is pink noise may not mean the same to all. ;-)

--
*Modulation in all things *

Dave Plowman London SW
To e-mail, change noise into sound.

Help with understanding pink noise results
 

Dave Plowman (Ignorant Nutcase) wrote:


I have a digital equaliser which generates what it claims to be pink noise
- and uses that to auto-eq a speaker system. It's very different from the
pink noise Audacity generates.

My feeling is pink noise may not mean the same to all. ;-)


** Pink Noise is a general term for any random noise that has the characteristic of equal energy per octave - as opposed to "White Noise" which has equal energy in equal amounts of bandwidth.

However, a given pink noise source will have band limits - a lower and upper frequency beyond which the noise is no longer "pink" or of constant level. When represented on a scope screen, pink noises with different band limits look very different.

Also, pink noise comes in small doses - such as of 1 octave or 1/3 octave too - in which case the centre frequency is quoted.


.... Phil

Help with understanding pink noise results
 

On 11/03/2015 13:59, Jim Lesurf wrote:

FWIW I checked the 'pink' and 'white' noise bands on a variety of test LPs.
They were all wildly different in ways that didn't simply mimic the
response of the cartridge I was using.

The best way I found to do measurements of frequency response was to use a
stepped or swept tone test band from a test disc.

http://www.audiomisc.co.uk/HFN/LP4/NewLampsForOld.html

shows some examples using the Analog Productions test LP.



The HFN test record I got doesn't have stepped tones, just a rather fast
10 Hz to 20 kHz non-linear sweep. This results in a 'tilted' 10
dB/decade spectral response curve like the pink noise test.

BTW the variety of FR results in your article was interesting and put my
own results into some context.