3D Sound

TheAudiophileDutchman · 3 Oct 2005

Hi Tom,

One way to do 3dsound would be using short FIRs and convolution in the time domain:

See for example the HRTF plug-in at: http://www.savioursofsoul.de/Christian/

By the way, convolution in the time domain is very time consuming for longer FIRs (let's say >>50-100 samples). Therefore for reverb applications, FFT and iFFT techniques are being employed in all commercial convolution reverbs that I know of. A freeware convolution reverb with high-latency (not realtime) can be found here: http://www.knufinke.de/sir/index_en.html

Tom7777 · 3 Oct 2005

Thanks for the links Arjan Schuurman 🙂

sequencer · 3 Oct 2005

Hi Tom (Dan)

The old way of achieving such effects as distance is to roll off the upper frequency as your virtual distance increases. This is in line with the real world effect of sound through air absorbing the upper frequencys as distance increases. ( possibly logarithmic to distance, but not sure). I almost forgot, it's obvious but also sometimes forgotten, lower the volume as distance increases. You can further achieve a distance effect by use of Reverb (but then it's assumed that the sound has lots of things to bounce around on before it reaches you).

The old way of achieving top to bottom (height) effects is that BASS is at the bottom and the Higher the frequency the closer the top of the soundstage. Again this is based on the real world because of the way the ear and body percieves sound.

These are Mixing Engineers (done a course,never used it for an income though, so what do I know) cheats if you like, although having DSP achieve it via HRTF and the like is much better to a degree, especially if using headphones.

I think the Roger Waters albums feature 3D sound a lot which I believe was achieved via the above rules and also using EQ for altering the phase of the sound. A desk EQ alters the phase of sound passing through it anyway by nature of the electronics envolved. I think that the effects kind of pre-date DSP availabilty. Can't say I've heard these albums though as Mr Waters is not my cup of Char.

Hope you manage to achieve your 3D sound somehow.

Sequencer 😀

Tom7777 · 4 Oct 2005

Thanks sequencer, that information helps me a lot 🙂

Tom7777 · 4 Oct 2005

I have been able to get a bit of 3D depth into the sound, its very hard to do well though as you can change the audio when using reverb and highpass filters ect, the effect i have at the moment is quite close sounding and im still trying to work out how to give the sound the distance, the lower volume on out works ok right now but filtering the sound to be behind or in front of the headphones is not working so great just yet but im getting there 🙂

sequencer · 5 Oct 2005

Hi Dan,

There are several other things that need to be taken into account when listening through Headphones (didn't want to complicate matters before and give too much input to ya). Sound in headphones has an unnatural soundstage because each ear is isolated from the other.

When listening to music without headphones on, i.e. with loudspeakers, the ears recieve a full signal from each loudspeaker in front of them (left speaker transmits a full signal to the left ear and vice versa), however the opposite ear also receives a slightly delayed (about 300 microseconds) and level reduced (about 10dB less)signal. There is also a comb filter effect coming into play on the opposite ear because its effectively in a shadow caused by the skull. There is a good bit of info at the following site:

http://www.headphone.com/products/faqs/about-headroom-crossfeed/

When I asked a couple of weeks ago about FIR filters, I had in mind to use them for a Headphone crossfeed circuit. I have already built such a thing within Quantum FX, although to be fair I'm still testing the sound and tweaking it.

Good luck with the project.

Sequencer 😀

Tom7777 · 5 Oct 2005

Ahh ok, this may well be the reason why it doesn't sound amazing right now becuase i work with audio via headphones only and did not know about this, i will test it with the speakers and see if i can get a better result, thanks for your help 🙂