Another thing that was discussed in the Reviews forum was the idea that it could possibly use the mic input to detect ambient noise, and increase the agressiveness of the compression as the road noise increased. That would be awesome.

<delurk>
Even better - generate an inverse signal for noise cancellation. Would that work? Now that would be incredible.
<relurk>

Borislav

This is something that has crossed my mind from time to time too.
Don't know if something like this WOULD work?
Anyone who have any thoughts???


TommyE

Noise cancellation is a huge problem. Many auto manufacturers have attempted something like this. It is a very sensative process. The biggest problem is you have to monitor the placement of your ears (not really as necesary in a car) to adjust the phases for every frequency across the spectrum. Another problem is a cancelled noise for the person in the front seat may be doubled in amplitude for a person in another seat. These problems have no effect for noise cancelling headphones, this is why they work as well as they do.

Alex Lear

All of the audio settings have two personalities (home and car) and I don't see why dynamic compression would be any different.

Rob

Noise cancellation is an established technology, but it tends only to be really effective in very specific or controlled environments. You can cancel a lot of prop noise in a small plane because you know the cabin dynamics, but cancelling generic noise in a generic car cabin would be an entirely different kettle of fish.

I believe that some auto manufacturers are researching this (maybe there are even early systems on the market, I haven't checked recently) but they have an advantage because they're designing for a specific model and audio system.

Rob

All of the audio settings have two personalities (home and car)

Not entirely true, Rob:
There's only a single loudness setting (home and car), which IMHO doesn't make sense.
Bug or oversight?


Henno
mk2 6 nr 6

Oversight I guess.. report it! :-)

(I know you just did, but if you email it I won't have to try to remember it in the morning!)

Rob

I envisioned having the volume pop up screen with both a minimum and maximum bar (basically the same as now, with another bar next to it), and then being able to adjust those. Anyone think this would confuse people?

Er, I'm still probably not explaining this correctly, it's like this http://rmitz.org/example.gif. The text would presumably also have to be changed.

Fly me to the moon...

Interesting idea, but there's more parameters to a compressor than just the minimum threshold.

And technically, the compressor has nothing to do with the volume. It just compresses the source wave data without altering the volume setting.

___________
Tony Fabris

I know that this isn't quite how the current version of the code works, but as rjlov said, this is the model he wants to move toward. Unless I misunderstood him, of course.

Fly me to the moon...

Lexus has done work with noise cancelation a while ago. While they can't cancel *any* noise in the cabin, they can cancel the engine noise actively and passively. They use noise absorbing materials to reduce noise down and then after that they can cancel most of the remaining engine noise actively.

Calvin

Does this answer your question?

Yeah, and then some! Thanks!

I do have a question about normalization in Audio Catalyst. In its' normalize option, it says "Normalize to [a percentage]" and then says "but only if the track is lower than [a percentage] or higher than [a percentage]"

Does that "lower than" have anything to do with bringing the noise floor up? These are the setting that confused me as to how voladj would help. It SOUNDS (from reading the options) like it's bringing the noise floor up and the peak back down. Is this not the case? If this *is* the case, isn't this what you just described, except that voladj does it in real-time? Perhaps there's more going on than only this in voladj, but that's the BASIC (not to diminish the work on it!) piece, isn't it?

George

normalization in Audio Catalyst

Hi George,
I too was confused by the AC options when I started to rip for my empeg. Now I find the AC options for 'Variable Bit Rate' and 'Normalisation' very useful. This is the way I believe it works:

Normalisation will adjust (bring up or down) the output level of the entire track by the same amount. To do this, AC will listen to the entire track and find the peak recording level and, if this falls within the boundaries that make normalisation worthwhile, adjust the volume of the entire recording equally. I like to think about this as the binary representation of floating point numbers: I imagine that normalisation leaves the fraction alone (content remains unchanged) but adjusts the exponent (the multiplier i.e. volume) of the frames such that the peak equals the percentage of max output that you set.

I now have this normalisation option on all the time when I rip for the empeg player and have noticed that most new CD remain untouched: they don't need adjustment: almost all are mastered in a such way that max output is at 98% or 99%. Older stuff, however, is sometimes put on CD at much lower levels, and therefore sounds less loud too. To listen to these CD's you'd need to adjust the volume of your head unit / pre-amp. Normalisation will allow to bring such older recordings up to the same volume level as the new stuff, so that you won't have to adjust the volume of your empeg player (as much) between tracks. In theory you ask AC to normalise to any level, so you can also normalise recordings down to say 70% or 50%, but I see no benefit in doing this. During play-back you'd need to amplify these more / introduce more distortion.

My understanding of Richard's 'Volume Adjust' is that it looks ahead to see if the output level of what's going to be played next is significantly different from what's currently playing and, if so, smoothes out the differences. As a result, low volume passages are turned up a bit and when if finds sudden increases in output level, it quickly turns down the volume to avoid clipping. (I don't know if Richard manipulates the empeg volume, of the output level data in the recording. I would think the latter.)

In this way Richards utility complements normalisation: AC's normalisation will smooth out differences between recordings, but leaves the soft/loud differences in tact. Richard's 'Volume Adjust' will smooth out the differences, such that the low passages are not lost in the back ground noise.

Henno
mk2 6 nr 6

Does that "lower than" have anything to do with bringing the noise floor up?

I'm afraid not. The text in the dialog box is misleading.

Currently it says: "But only if the track is lower than (x) or higher than (x)", When it should actually say: "But only if the TRACK'S PEAK is lower than (x) or higher than (x)".

All it does is look at the single highest peak in the track, then add a multiplier to the whole track based on those criteria. Personally, I normalize everything unconditionally to 100 percent. Although it helps some older albums that weren't fully normalized, for the most part it does nothing because most albums are already normalized. I'd say that out of my entire CD collection, there were maybe two or three CDs that benefited from this.

Normalization doesn't usually fix the perceived-volume differences between tracks because most of those differences are due to differences in the amounts of compression in the mastering stage.

___________
Tony Fabris

Okay, I think I finally understand this. Richard's program adjusts it dynamically, meaning it raises the lows ONLY and raises the the highs ONLY, when necessary. Audiocatalyst does both of those, regardless and not in proportion to the part that's playing, it's adjusted the same amount throughout the entire track. If this were drawn on a graph, you'd have the track shown as a straight bar across the middle, representing the original sound. Audiocatalyst would have two identical lines running the length of the track, one across the top and one across the bottom, with the peaks and pits at the same points on both the top and bottom. Voladj would have two independent lines across the top and bottom, with the peaks and pits at different points.

I think that makes sense. If not, it does to me!

George

Just a "Me too". I have downloaded the V1 vol adjust kernel to my Mk I and it is great. thanks for that.

PeterH
" 'tis better to be silent and thought a fool than to speak and remove all doubt"