multi channel audio sender control unit (bpm synced patterns)

[davepenney]

Hi there,

I’m working on a multimedia project, which will split music into different freq bands, to say isolate a snare, and other sounds.

What I then need to do is have a control unit that is synced with bpm that can run a pattern and send these separate sounds to different amps/speakers, thus to achieve a mad mash up bizarre surround sound effect.

Could anyone offer any advice as to how this would or could be done or if there is a similar project/product around?

Thanks, dave.

 

[pinkmouse]

As this sounds like a school/college project, I will just say google band pass filters.

 

[davepenney]

thanks, however the concept for a multiple bandpass filter, isn't where im stuck.

its how to automate the rapid switching of these signals between several amplifiers, in sync with the actual audio source.

I can use a bpm output of an effects unit to give me the clock signal, but thats where I could do with some pointers to help design a circuit.

 

[macboy]

You may have a harder time than you think you will, trying to isolate individual sounds from a single source. This is especially true for percussion instruments (you mentioned a snare as an example). Percussion instruments tend to produce sound over a broad range of frequencies. Making the task ever more difficult is that most drums overlap the human vocal range. Don't forget, too, that all instruments produce harmonics (multiples of the fundamental frequency, or note being played), and it is largely the characteristics of these harmonics that make each instrument sound unique. Any bandpass filter narrow enough to even come close to isolating a sound will remove most or all of the harmonics, making the resulting sound unidentifiable.

I don't want to discourage you from pursuing this, I just wanted to give you a realistic picture of what you can expect the sytem to do, and what it will not do. Even though you will separate different harmonics of each instrument into a few different frequency bands, and they will be played back in different speakers, maybe that's OK because the listener's brain will still reconstruct the sounds.

You will need to build some kind of beat detector, one for each frequency band. And then you will need to use the output of each beat detector to trigger some switching circuit to change to a different output for that band.

Do do the switching, you could use an electronic switch (one per freq band) like the CD4051 (or 74HC4051, etc.). This is a one input, eight output mux. You select the output channel with a 3-bit binary input. The tricky part will be: how do you select what the next output will be, and how/when do you trigger the output to switch. The answer to the latter has to do with the beat detectors mentioned earlier, but you need to make sure not to switch in the middle of loud sounds and/or cause pops and clicks. The former question, poses another big challenge. Maybe you could use some kind of free-running binary counter, and latch (capture) the output using the beat detector, and send this (essentially random) number to the analog switch to choose an essentially random output each time.

Good luck

 

[davepenney]

Thanks, that helps a lot.

I was just thinking maybe this is the wrong way to approach it, maybe it would sound much better, and be a hell of a lot simpler, if instead the same audio is sent to each amp, but a control unit simply alters the volume of the separate signals in quick random succession, similar to when you mess around with the balance control on mixers.

But in this case say 6 channels instead of 2.

With this system predominantly being used with dance music, allowing say the kicks and snare to ‘dance’ around the room, would also eliminate the pops and clicks.