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Headphones and surround sound


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#1 Milcho   Crossbones+   -  Reputation: 1177

Posted 14 February 2013 - 11:20 AM

This topic has always bugged me.

 

The human brain distinguishes sound direction from 2 factors:

1. Sound latency - meaning the difference in time that the sound arrives in one ear vs the other ear

2. Sound volume - the difference between how loud the sound is in each ear.

 

I understand latency is mostly used for lower pitch sounds, and volume is used for high pitch sounds.

 

So, given this, if you're wearing headphones - just regular headphones that take stereo input - you can simulate surround sound pretty accurately. Don't believe me? http://gprime.net/flash.php/soundimmersion - sort of an old link too, from more than 5 years ago i think. Just plug in normal headphones in your PC and close your eyes.

 

So, basically sound can be recorded in such a way that when listened through headphones it sounds like surround sound. The reason its not, I suppose, is because the same sound can be listened through speakers - which don't need that sort of thing to sound surround sound, they already are physical objects.

 

But you can take regular stereo sound tracks and apply digital processing to make it sound like virtual surround sound in your headphones. This is what Dolby Headphone processing does, afaik.

 

Basically, this means that any headphones claiming to be 7.1 or 5.1 that have multiple speakers in them are really just a marketing ploy, since I doubt they give any advantage over regular stereo.

 

But most importantly - Why are not more manufacturers of portable music players (I'm looking at you Apple and Microsoft) not putting this feature in their devices!?

 

And why is it so hard to find headphones that are Dolby Headphone certified! 

 

Anyway, rant aside - do any of you happen to know of any good headphones that include this feature? I know there's a few listed on Wiki, and I can certainly google some - and I owned one pair once, some time ago, but it broke, and I've been meaning to find a quality one ever since, so I'm looking for someone who's had some experience. :)



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#2 minibutmany   Members   -  Reputation: 1648

Posted 14 February 2013 - 03:12 PM

But most importantly - Why are not more manufacturers of portable music players (I'm looking at you Apple and Microsoft) not putting this feature in their devices!?

 

Looking at Dolby Headphone processing, it requires the audio file to be surround sound, it can't just convert your typical MP3 file into surround sound.

I'm guessing they don't implement the feature either because this surround sound audio files might take up too much storage space or that the feature might not be used because most music is recorded in regular stereo anyways. Unless you watching movies maybe?

 

Any "Surround Sound" headphones that only have a regular 1/8 or 1/4 inch plug on them are fake, because that's just regular stereo sound. true surround sound headphones would need more than two channels. 


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#3 Milcho   Crossbones+   -  Reputation: 1177

Posted 14 February 2013 - 03:44 PM

Looking at Dolby Headphone processing, it requires the audio file to be surround sound, it can't just convert your typical MP3 file into surround sound

Actually it can take regular stereo and transform it into "virtual" soundstage stereo - as if you're actually listening to speakers. And most tracks are already stereo, so it seems like it would be a common thing. And it sounds really cool too, at least from the short time I had those headphones.



#4 frob   Moderators   -  Reputation: 22235

Posted 14 February 2013 - 04:25 PM

The surround sound stuff you pointed out are just ways to alter the sound sources so the stereo output sounds like more positional audio.



The tracks are already recorded in stereo. The original audio tracks may already have those same operations applied.

If you listen to movie soundtracks on headphones you will frequently hear the same effect you linked to without any special processing required.

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#5 Milcho   Crossbones+   -  Reputation: 1177

Posted 15 February 2013 - 02:27 AM

If you listen to movie soundtracks on headphones you will frequently hear the same effect you linked to without any special processing required.

 

I've always thought that that sort of processing is not applied to any soundtrack before hand - mainly because the processing seems only useful when you listen to the sounds via headphones. I'm not sure if you listen to a track like this via speakers, whether it would sound just as good, or at least, better than just regular stereo - speakers obviously don't need this sort of processing since they're already spatially positioned in relation to your ears.



#6 Aressera   Members   -  Reputation: 1460

Posted 15 February 2013 - 02:43 AM

Actually, the human ear perceives more than just differences in time of arrival and intensity. The transfer function of the human ears in a given direction is given by an HRTF which will consist of a complex FIR filter that will probably have frequency components. If you have a suitably sampled HRTF (with many directions) you can simulate surround sound using headphones. The audio system convolves the appropriate HRTF filter with each input channel to produce the surround-like audio.

 

The primary issue with this is that everyone's head is a little bit different and so if you get an HRTF for person A, it won't necessarily sound correct if person B listens to the sound using that HRTF. In addition, HRTF processing is somewhat expensive and takes some non-trivial CPU to do in real time for longer high-quality filters.

 

Finally, there would be no point in taking a stereo source file, upmixing it to 7.1 or whatever, then filtering each of the 8 channels with the appropriate HRTF, then downmixing back to stereo. The coloration and phase cancelation from this would probably sound terrible! This would only be viable if your source audio has surround information to start with.



#7 Milcho   Crossbones+   -  Reputation: 1177

Posted 15 February 2013 - 04:07 AM

HRTF is exactly what's used by Dolby Headphone to generate the audio as a faux-positional source. I'm not 100% familiar with the technology behind it. The real time conversion is achieved using a finite impulse response filter (to quote dolby's site: "Dolby Headphone technology also provides all the benefits of a highly detailed finite-impulse response (FIR) filter, with virtually no latency.")

 

I suppose that strictly speaking HRTF is more than sound latency and volume - the way a soundwave reflects from your ear lobe, as well as the way you receive the sound changes when you move your head are things that headphones probably won't be able to simulate correctly. (interesting topic btw, I've started reading more and more about it now)

 

However, you can take 2 channel sounds and apply this sort of processing to it, even if it does not contain all the necessary information for full blown HRTF. It works fairly well in my opinion. When I had a chance to test this with my headphones, I had two unplugged speakers standing in front of me, and when the dolby feature was enabled, I could swear that the sound was coming from the speakers, and not from the headphones. 

 

My main gripe is why this isn't a more commonly seen thing - I suspect that people generally aren't sure how a pseudo positional sound like that sounds when they try headphones, and are probably not willing to spend the extra buck on headphones like that. 

I really want to try to find a decent pair of headphones. The ones I had before required software on your pc for the processing, and I want to see if I can find ones that work with anything!

 

Edit: After digging through some headphones, this is probably close to the pair, if not the exact pair, i had: http://techreport.com/review/19740/corsair-hs1-gaming-headset


Edited by Milcho, 15 February 2013 - 04:19 AM.


#8 Hodgman   Moderators   -  Reputation: 31017

Posted 15 February 2013 - 06:08 AM

The human brain distinguishes sound direction from 2 factors:
1. Sound latency - meaning the difference in time that the sound arrives in one ear vs the other ear
2. Sound volume - the difference between how loud the sound is in each ear.

This would be true if your ears were just holes in the side of your head, but if you cut off someone's ears so this is true, then they will have really bad hearing. The shape of the ear itself is critical, as it funnels in sounds and also changes them depending on their origin. The HRTF is mainly about the geometry of your inner and outer ear.

 

Basically, this means that any headphones claiming to be 7.1 or 5.1 that have multiple speakers in them are really just a marketing ploy, since I doubt they give any advantage over regular stereo.

No, unless you've had a HRTF custom-made for your own ears (which is possible to calibrate, but very time-consuming), and a fancy driver that can accept this HRTF, then multi-speaker headphones are the next-best thing (actually, a multi-speaker headphone combined with a user-calibrated HRTF would probably be the best thing). As well as software processing to add origin-related hints (volume, latency, etc), they also allow your ear to do what it does in the real world, and change the incoming sound itself depending on the direction it came from, in the exact way that your brain has calibrated itself for over a lifetime of hearing things.

 

But most importantly - Why are not more manufacturers of portable music players (I'm looking at you Apple and Microsoft) not putting this feature in their devices!?

What's the point? Yeah, you can convert a stereo signal so that it sounds like it's coming out of speakers that are 5 foot apart, 10 feet in front of you... but why? I'm happy to hear my stereo music as if it's inside my skull, rather than as if it's coming from speakers in front of me. I'm also happy to hear it from actual speakers that are actually in front of me wink.png

 

Now for games and virtual 3D worlds, surround sound is actually important, so emulating surround sound on cheap stereo headphones with advanced HRTFs -- that is a good idea.


Edited by Hodgman, 15 February 2013 - 06:12 AM.


#9 Milcho   Crossbones+   -  Reputation: 1177

Posted 15 February 2013 - 06:29 AM

I haven't used surround sound headphones for more than a few minutes, but from my experience with stereo headphones and HRTF processing, my ears were still fooled that the sound was coming from an actual object outside my headphones.

Maybe the surround headphones provide a much better processing for that. 

 

For HRTF being mainly about ear geometry processing - I don't know about mainly - and my reading is more or less from Wiki - but you can achieve left/right distinction based mostly from latency and volume differences. More complete directionality, above/below/ front/back is affected by ear geometry as you've described.

 

What's the point?

I dunno, personal preference I suppose. I was listening to some tracks today with some effects coming solely from my right earpiece, and it bugged me, since I imagined what it would be if it was mixed properly, to at least give you a minor sense of direction. I just don't like some tune or sound that just keeps blasting in one ear and not at all in the other.For games definitely makes a huge difference, as you said. And sure it's personal preference, but not a lot of the people I met knew what the faux-surround sound through headphones sounded like - and if they did maybe they'd like it. 



#10 TheChubu   Crossbones+   -  Reputation: 4564

Posted 15 February 2013 - 08:03 AM

Play a mono track. You'll hear it as dead center. Delay one channel (left or right) by 20 ms and suddenly the sound will appear to come from everywhere :D (only for headphones cuz comb filtering and all that).


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#11 Milcho   Crossbones+   -  Reputation: 1177

Posted 15 February 2013 - 08:08 AM

Delay one channel (left or right) by 20 ms

Do you actually do this? Is there software that can delay the audio output of your sound card by channel?

Even if so, I don't have many mono tracks :P  and it'd be at best a curiosity, and sadly not a substitute for what I want



#12 minibutmany   Members   -  Reputation: 1648

Posted 17 February 2013 - 03:18 PM

I don't have many mono tracks

 

You don't even have Beach Boy's Pet Sounds?

This is a crime.


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#13 TheChubu   Crossbones+   -  Reputation: 4564

Posted 17 February 2013 - 08:31 PM

Delay one channel (left or right) by 20 ms

Do you actually do this? Is there software that can delay the audio output of your sound card by channel?

Even if so, I don't have many mono tracks tongue.png  and it'd be at best a curiosity, and sadly not a substitute for what I want

Well. It's actually something I do on FL Studio, with a VST. There are many freeware VSTs that can do such thing.

 

As for actually delaying one channel in your sound card. I have no idea. You could probably find a plugin for Winamp that does such thing. I think i have used this decoder in the past http://www.winamp.com/plugin/winampac3/221648 It says you can set up a delay per channel.

 

But yeah, it is a curiosity :D It doesn't sounds great for everything. I mean, you can't delay one channel of a song and expect it to sound good. It's used sparingly on a per-track basis when mixing audio, often with further processing so the sound doesn't filters itself out when played on speakers.


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