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Lowering the ‘Noise Floor’


lostwin
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13 minutes ago, JD68 said:

If you download a decibel reading app on your phone you can record the noise level in your room. Try doing it with total silence in your room and you might be surprised at the actual decibel level it picks up. Then try it with your system on but no music playing and see if the level changes. 

It would be interesting if we get a few people to try this and compare results, would this be a rudimentary way of comparing noise floors between systems?

I can’t help but think there is more to it than this though.

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1 hour ago, Lurch said:

I would say the best analogy is being in a bar and trying to listen to the news or commentary from the TV. The electrical background noise is similar to the background hubbub in the bar, with a rowdy lot in you have to really concentrate to hear however as the crowd quietens down so your more easily able to hear the telly. 

The electrical noise doesn't have to be audible but it will still mask information and as Joolz said, once it's gone/reduced you will know it. 

Just re-reading this John and I think it captures the juxtaposition that is probably leading to my confusion.

The TV in the noisy bar is a great analogy- clearly this is audible background noise masking the sound from the TV. How does this then align with the inaudible electrical noise suggested in your second part? If it is inaudible how does it mask the sound?

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Richard, 1st consider how small the initial signal is from an mc cart, before its amplified by the mc stage. It is at this point that the most masking can be done by electronic background noise (the point at which the music signal is weakest). The music signal plus the inaudible noise then enters the mc stage and is amplified before being passed to the mm stage for more amplification to get it up to the circa 2v needed by the pre-amp stage Inorder to drive the power amp section which drives the speaker. 

Therefore as you can see the cartridge signals quieter/more delicate parts are covered by electrical noise reducing the amount of detail that gets passed into the mc stage and then through the rest of the amplification chain. Also whilst the electrical noise is also amplified its already done the damage to the quieter parts of the signal and is below the level of the music it couldn't mask so is still inaudible even when amplified as the remaining music drowns it out. 

Edited by Lurch
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1 hour ago, andrew s said:

Then you need to explain what you think the "noise floor" is. To me it is the level at which noise takes over from the intended signal.

Regards Andrew 

This would not necessarily have to be the case. If even a low level of noise were present but out of phase with a low level note then it could diminish that note even though it was at a much lower level. 

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1 hour ago, JD68 said:

If you download a decibel reading app on your phone you can record the noise level in your room. Try doing it with total silence in your room and you might be surprised at the actual decibel level it picks up. Then try it with your system on but no music playing and see if the level changes. 

Just finished a listening session so checked readings with system on (no music) and off using a phone app. Reading was 26db average for both from the listening seat.

I do actually have quite a noisy system- transformer hum plus fan from mains regenerator so maybe the phone mic is not the best tool. 

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11 minutes ago, wHIZZY said:

This would not necessarily have to be the case. If even a low level of noise were present but out of phase with a low level note then it could diminish that note even though it was at a much lower level. 

Noise is normally random in amplitude and phase so yes you might get occasional happy coincidences but normally not. Regards Andrew 

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18 minutes ago, andrew s said:

Noise is normally random in amplitude and phase so yes you might get occasional happy coincidences but normally not. Regards Andrew 

Agreed if the noise was indeed random.  However, if the signal (music) itself was the cause of the generated out of phase component or 'noise' then it would not be random and you would never hear the out of phase component (noise) when no music was playing.

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25 minutes ago, wHIZZY said:

Agreed if the noise was indeed random.  However, if the signal (music) itself was the cause of the generated out of phase component or 'noise' then it would not be random and you would never hear the out of phase component (noise) when no music was playing.

Then that would be harmonic distortion would it not if it were of the same frequency and intermodular distortion if of different frequency. These "noise" components are normally considered separately from random noise.

Regards Andrew 

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4 hours ago, lostwin said:

With the excellent discussion on imaging, I would be interested to get thoughts on another hifi staple, the ‘noise floor’.

What exactly does lowering the noise floor mean and what difference does it make to what you hear?

Noise floor in a piece of equipment is the operating noise level. Signal-to-noise ratio is the difference between the signal and the noise.

In your room noise floor is the background noise level.

Lowering the noise in the listening room or the system will make low-level sound more audible, decay more noticeable and longer, detail more intelligible and less tiring.

4 hours ago, lostwin said:

I am particularly interested when used in connection with improvements  heard with turntables, but does a common definition apply to all pieces of kit in the chain?

A digital source is the first step to improving the signal-to-noise ratio. But if you listen to vinyl you could perhaps start by seek out a very transparent phono preamp which will make changes/improvements to the turntable and cart more noticeable.

Soundproofing your room will reduce background noise, as will moving to a detached house or the countryside.

Edited by tuga
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I

43 minutes ago, andrew s said:

Then that would be harmonic distortion would it not if it were of the same frequency and intermodular distortion if of different frequency. These "noise" components are normally considered separately from random noise.

Regards Andrew 

I think the original question was just about lowering the noise floor, not just random noise. I'm certainly not clever or knowledgeable  enough to identify or name the cause of any out of phase noise component generated by the original signal but I certainly believe it could exist.

Whatever it's mechanism of generation. The main point being it would only be present when the signal (music) was playing and therefore could not be heard as hiss, hum or other when no signal was present. As such it would almost seem not to exist. 

Edited by wHIZZY
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1 hour ago, lostwin said:

Just finished a listening session so checked readings with system on (no music) and off using a phone app. Reading was 26db average for both from the listening seat.

I do actually have quite a noisy system- transformer hum plus fan from mains regenerator so maybe the phone mic is not the best tool. 

You could try this test instead, setting the voice-over volume to a comfortable level:

Dynamic Test Tones

Determine how much dynamic range is masked by your room's noise floor.

https://www.audiocheck.net/testtones_dynamic.php

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In my experience nothing lowers the noise floor quite like my two AC power cords. 

top notch equipment isolation.  

thirdly a decent power supply upgrade if available .. 

Edited by 2010*zuma
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12 minutes ago, 2010*zuma said:

In my experience nothing lowers the noise floor quite like my two AC power cords. 

top notch equipment isolation.  

thirdly a decent power supply upgrade if available .. 

Edited by 2010*zuma
Opps done a doubler mods please delete
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I’m still confused!

some great replies but to me quite a few different interpretations - room noise, electro mechanical noise from the equipment, electrical signal noise from the mains etc.

Also seems to be two different concepts as to how this impacts what hits your ears. One where the quality of musical signal itself is diminished through the system chain and the other where the signal is what it is but exterior noise masks your ability to hear it.

Does that mean the noise floor has a broader more generic meaning?

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16 minutes ago, lostwin said:

Does that mean the noise floor has a broader more generic meaning?

From Wikipedia "In signal theory, the noise floor is the measure of the signal created from the sum of all the noise sources and unwanted signals within a measurement system, where noise is defined as any signal other than the one being monitored.:"

So the above views just cover different subsets (sources) of  noise. 

Regards Andrew 

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