hello gang, i just registered today, and i'm quite interested in the topic. i rather new to the topic and i possess no degree sound recording , so if i sound a little "blonde", do forgive. i've read a few articles about infrasound and i's become a big fascination of mine... that, and ghosts
here'z tha catch:
i'm a musician, and i want to record various infrasounds and put them in my music. i want to amplify the infrasound so you can hear it, but i also want the unhearable version so it could be played from a special set of speakers that can emit its frequency.
soooooo my question is: where can i get a quality mic and speaker that can capture and produce these sounds? um, same goes with computer software... can MIDI pick up on the unlistenable infrasounds? can recording on a vinyl record capture these sounds? if not what can?
You are not going to be able to do this in a conventional manner. Audio amplifiers, even high end amps genrally don't reproduce below 20 Hz. This is the low end of hearing. There are special DC amplifiers which will process these frequencies, but almost no one who would be listening to your music would have equipment capable of reproducing them.
But assuming you want to do this, a condenser mic should be able to capture these low frequencies. (Not the little electret mics you find in consumer equipment, I am refering to professional grade ribbon mics. ) Next you will need a DC operational amplifier to boost the levels. Standard amplifiers like you find in audio gear generally use coupling capacitors which will block extremely low frequencies. Direct coupled amps will pass them. Recording can be done using digital since analog tape also suffers from rolloff at sub audio frequencies. Digital has the advantage of being able to record down to DC levels (Vinyl can capture these low frequencies, but no pickup cartridge has sufficient low end response to capture them from the record. Plus there are tone arm damping factors which would prevent this from being practical.) Speakers are not a real problem as long as you are using a direct coupled amplifier in playback as well to drive them.. Any large loudspeaker will reproduce infrasound, but the larger the speaker cone the better. It should also be mounted in an airtight enclosure for best results.
Now, may I ask, why do you want to do this?
Sounds to me like an experiment in psychoacoustics....create a paranormal feeling. Its been done....but no standard consumer gear will reproduce it. In my professinal work I use good pro gear, all Harmon Family stuff, JBL, AKG, Crown....Crown Class D amps, DC.....they won't pass below about 15 HZ. Why? Filtraction to prevent low frequency oscilations that destroy speakers. interestingly, you can put a 60Hz signal into a Crown CTs 3000 and run your electric drill through the outputs. You can also take welding rods and attach to each output via wire and draw large sparks. The amps survive this abuse just fine. In fact, this is done to demonstrate the protection circuitry in the amps. But they will not amplify infrasound. Most infrasonic measurements are made with either a measurement mic or a geophone, run through a special preamplifier, then displayed on software. No matter what one does to it, it will not be heard, thouch it may be "felt".