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Apologies if this topic has appeared before...

 

I listened to Sunday Half Hour yesterday and noticed appalling changes in volume (compression?), so that any increased loudness in the music resulted in the volume being momentarily attenuated. I have noticed this before, especially on ClassicFM, where, for example, the last chords of the Widor Toccata are horribly reduced in impact. In choral music, any soaring treble lines induce the same effect.

 

As a keen audiophile, I find this really frustrating.

 

Can anyone explain to me why this has to be so ? I tried listening via DAB and on FM but found the same result.

 

H

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Apologies if this topic has appeared before...

 

I listened to Sunday Half Hour yesterday and noticed appalling changes in volume (compression?), so that any increased loudness in the music resulted in the volume being momentarily attenuated. I have noticed this before, especially on ClassicFM, where, for example, the last chords of the Widor Toccata are horribly reduced in impact. In choral music, any soaring treble lines induce the same effect.

 

As a keen audiophile, I find this really frustrating.

 

Can anyone explain to me why this has to be so ? I tried listening via DAB and on FM but found the same result.

 

H

 

Hi

 

It's because most radio stations - including BBC radio 3, at least on FM - insist on using "Optimod" processors so that the volume is kept up. The "excuse" is that it's for the benefit of those listening in cars. The real reason stems from American commercial radio, when everyone wanted to be the loudest station on the dial to attract more listeners and hence more advertising revenue. Gone are the days when radio was a "hi-fi" medium - although I understand that radio 3 at least, and maybe the other BBC stations aren't processed in this way for the feeds via the Sky sattellite - and the bit rate, and hence the audio quality - via Sky is higher than either DAB or DTT, so for quality, that's the way to go.

 

That said, if the processing was as obvious as you say, then possibly something needs adjusting - a complaint to the stations might just help - but I doubt it, as quantity seems to be more important than quality in broadcasting these days.

 

Every Blessing

 

Tony

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It's because most radio stations - including BBC radio 3, at least on FM - insist on using "Optimod" processors so that the volume is kept up.

I have a bit of a theory about this. I believe the result of this compression (the 'backing off' of the volume) is analogous to that done by the human ear at considerably higher volumes. Is it possible that this effect fools the brain into thinking that volumes are louder than they are, therefore increasing listening fatigue?

 

(This is a totally unscientific and unsupported guess of an idea. Make of it what you will... :lol: )

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I have a bit of a theory about this. I believe the result of this compression (the 'backing off' of the volume) is analogous to that done by the human ear at considerably higher volumes. Is it possible that this effect fools the brain into thinking that volumes are louder than they are, therefore increasing listening fatigue?

This is consistent with my recent remarks about unnatural recording techniques increasing listening fatigue.

 

Paul

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I have a bit of a theory about this. I believe the result of this compression (the 'backing off' of the volume) is analogous to that done by the human ear at considerably higher volumes. Is it possible that this effect fools the brain into thinking that volumes are louder than they are, therefore increasing listening fatigue?

 

(This is a totally unscientific and unsupported guess of an idea. Make of it what you will... ;) )

 

Hi

 

And a very good guess. Compression is used in recording for two reasons - firstly, to even out changes in dynamics, and secondly, as with most current radio broadcasts, to make things sound louder (think TV adverts - the actual peak sound level is the same as the surrounding programmes, but the adverts always sound louder because they usually apply heavy compression, so the average level is higher than natural).

 

Both uses are unnatural and can lead to fatigue.

 

Every Blessing

 

Tony

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Apologies if this topic has appeared before...

 

I listened to Sunday Half Hour yesterday and noticed appalling changes in volume (compression?), so that any increased loudness in the music resulted in the volume being momentarily attenuated. I have noticed this before, especially on ClassicFM, where, for example, the last chords of the Widor Toccata are horribly reduced in impact. In choral music, any soaring treble lines induce the same effect.

 

As a keen audiophile, I find this really frustrating.

 

Can anyone explain to me why this has to be so ? I tried listening via DAB and on FM but found the same result.

 

H

 

The problem with the end of the Widor Tocatta is that the 32ft is, to a microphone, very loud, and the limiters in the broadcasters studio cut the volume to compenstae. So the high F disappears when the pedal re-enters. Radio 3, I believe, overcomes the problem by not broadcasting the very low frequencies at 'full stretch', but attenuates them. Certainly they seem to have less of a problem the Cfm do.

 

Regards to all

 

John.

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Yes the problem is all to do with the way the signal is treated before it's sent to some of the output feeds. The 'Optimod' system is a paricular type of level compression system that has been in use since the 80s when when I was a BBC engineer (I didnt' like Optimod, I hasten to add!). It quickly became popular among independant broadcasters before the BBC used it. The BBC decided to start using Optimod when they realised that pop chart material on a certain commercial station sounded more effective on a portable radio than the same material received from Radio 1 on the same radio. I seem to remember that the Radio 3 FM feed didn't go through the optimod system at that time although the other FM feeds did. The AM feeds had an even higher level of treatment (all networks were also broadcast on AM at that time).

 

The problem with non pop music content is that any but the slightest compression is potentially ruinous. The overall amount of compression is the problem rather than the 'optimod' system particularly. As the thread starter has already said it is frustrating at the climax of a piece of music when it sounds as though the volume is being turned down especially as more notes and perhaps other sounds come into play. A significant related factor is that the gain reduction is not instantaeous but relatively slow (by design). This means that sudden loud sounds can go through without being affected (such as a drum) but a sustained louder sound gets pulled back about a fraction of a second, never to return to its original level.

 

John R

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Yes the problem is all to do with the way the signal is treated before it's sent to some of the output feeds. The 'Optimod' system is a paricular type of level compression system that has been in use since the 80s when when I was a BBC engineer (I didnt' like Optimod, I hasten to add!). It quickly became popular among independant broadcasters before the BBC used it. The BBC decided to start using Optimod when they realised that pop chart material on a certain commercial station sounded more effective on a portable radio than the same material received from Radio 1 on the same radio. I seem to remember that the Radio 3 FM feed didn't go through the optimod system at that time although the other FM feeds did. The AM feeds had an even higher level of treatment (all networks were also broadcast on AM at that time).

 

The problem with non pop music content is that any but the slightest compression is potentially ruinous. The overall amount of compression is the problem rather than the 'optimod' system particularly. As the thread starter has already said it is frustrating at the climax of a piece of music when it sounds as though the volume is being turned down especially as more notes and perhaps other sounds come into play. A significant related factor is that the gain reduction is not instantaeous but relatively slow (by design). This means that sudden loud sounds can go through without being affected (such as a drum) but a sustained louder sound gets pulled back about a fraction of a second, never to return to its original level.

 

John R

 

Hi

 

Radio 3 started using Optimod a few years ago - initially just in the "drive time" slots, but now, I gather, it's in the signal chain all the time.

 

Every Blessing

 

Tony

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