Posts by 142

Re: "The term "audio quality" just isn't applicable"

True: profit's the goal - But why the hell would they waste money on an engineer if audio quality doesn't matter?They pay them those prices because of the quality of the results.

Re: "The term "audio quality" just isn't applicable"

LOL... You do know the people mix-engineering the top tracks in those genres are making £20,000 per track at a minimum? Do you honestly think record companies would pay that much if the results wen't good? You're just letting the artist's "image" dictate what your ears think they hear.

Re: Mutually assured dullness

If they all go to war, and it ends up with a division again along the 38th parallel, with the Chinese taking responsibility for repairing the north, and the US taking responsibility for rebuilding the south...... :-(

I really wish that was more unimaginable than it is...

Re: Mutually assured dullness

Yep. The danger here is that if it does go nuclear, something could wrong, causing China and/or Russia to get involved against the US. It doesn't strike me as at all impossible that an ICBM from the US could accidentally hit either of those countries instead of NK. Then what would happen? Something as a bad as this: http://www.johnstonsarchive.net/nuclear/nuclearwar1.html ? Half as bad? Quarter as bad? Does it make a difference?

I, for one, don't want to find out.

Re: "partly because these don't exist"

Hmmm... unfortunately it's a safe bet that these "don't exist" in the same way Israel's nukes "don't exist".

But you're right there's no chance that China would be that stupid. The scenario is so idiotic on so many levels it baffles me how our liveleaker could have come up with it even as a piss take!

Re: Holodecks aren't just about processing power

Surprisingly, roughness / solidity isn't the most difficult thing to simulate. Bizarrely our ears over-rule our fingertips in this context! Blindfold someone with headphones on, and have them scrape their hands over a piece of glass, and they'll be completely convinced it's wood, metal, sandpaper, or marble they're touching depending on what sound you feed into the headphones.

I've done experiments that have listeners utterly convinced they've just sat down into a plush fabric sofa, when in fact, they've sat onto something solid. It's amazing what careful sound design can do to fool people! :-)

Also - in a somewhat similar phenomenon, our sense of touch works determines the texture of material by detecting vibrations, and there's been a lot of progess in this field: http://www.science20.com/news_articles/sense_touch_uses_vibrations_just_hearing-98781

Re: rights collections agencies are right

Apologies for the garbled edit on the first line! "Asking them to collect"..

Re: In Audacity you can easily add a dehum filter

Yip. The trouble being though, of course, when you notch out that many harmonically related frequencies from a human voice, makes it sound like they're talking in a 10 foot diameter plastic pipe...

(Sherlock for his pipe fondness, not his sarcasm! ;-) )

Re: Good gods, Donald!

And about phase - If I set a signal generator to give me a 50Hz sawtooth wave, and I record that 50Hz sawtooth wave, I will get a phase-perfect 50Hz facsimile of the sawtooth wave. NOT, as you seem to be implying, a phase shifted mess of a waveform.

Good gods, Donald!

How inaccurate do you think modern digital audio gear is??

Mains frequency drifts, due to the phase shifts you're mentioning, between 49.9 and 50.1Hz. That's a piece of piss to record, and has been for probably 40 years! Indeed - you can audible hear the pitch change as you're working on audio with high levels of mains hum recorded over even a 15 minute period of time, if you jump back and forth between different sections. Hell, you can see it visually in the amplitude waveform, without even resorting to frequency analysis!

Don't believe me about the frequency variation? Have a look here - http://www.nationalgrid.com/uk/Electricity/Data/Realtime/Frequency/Freq60.htm

Re: Its even easier than Audacity

What, pray tell, are you going to do about the induced noise at, say, 800Hz?

Re: So take a high-pass 200Hz filter and ...

Errr... numbers aren't necessarily meaningly - a 48dB/Octave HPF 200Hz filter will push any noise at 50Hz well below the level encodable on a 16bit system.

But anyway, that's moot point - as I've just mentioned in a different post here - of much more interest when doing this sort of analysis are the harmonics in the 500Hz-3kHz range - not the fundamental. It's utterly impossible to remove the higher harmonics of mains hum without mangling the speech.

Re: muck up a 50Hz signal too much to arrive at a reliable forensic result?

"I'm just wondering if recordings made digitally with a system designed to attenuate/discard "unessential" information mightn't muck up a 50Hz signal too much to arrive at a reliable forensic result?"

They'll be fine for any real world codec - you're not likely worried about 50Hz when doing this sort of analysis - that's a difficult frequency to work with, especially if you're going to be trying to verify things aurally. Of much more interest is the harmonics - 100, 150, etc, up into the low-kiloHertz (speech) range which (annoyingly for any sound engineer) tend to get picked up much more strongly than the fundamental. It's easier to pick out and analyze frequency changes in those ranges. In the event your compression algorithm for recording ditched the 200Hz range, then most likely 400Hz, or 450Hz will still be there, and you can derive the fundamental from there.

Remember how Shazam can almost without fail pick out a recording in the background of a noisy restaurant through a crappy phone mic - that achievement is orders of magnitude more difficult than what the Met has in mind.

You make a fair point though, as it is possible to envisage compression with the sort of frequency quantisation where this sort of analysis will not work (quantising every frequency to, say, the nearest 100Hz for example, as in a crude FFT), however that sort of codecs will make any speech sound completely robotic - think somewhere between Stephen Hawking and a Dalek.