The science behind the TriPad is based on eliminating vibrations. You are sitting at your desk, a truck goes by. You hear the roar of the engine through the walls and feel the vibrations even though the cause can be 30 meters (100 feet) away. Sound is vibration. It travels in waves through gases like air, liquids like water, and through solids such as your office walls, car windows, studio floor and the earth beneath. To stop sound, you have to stop the vibration.
The TriPad is a simple isolation pad that mounts on a tripod microphone stand to isolate it from floor-borne noise. It works by floating the mic stand so that vibrations are decoupled. Because the floor, TriPad acoustical foam and the mic stand all have a different mass, this virtually eliminates their coupling sympathetically through the air. Once installed, noise that would normally travel through the floor into the mic stand is essentially dissipated in the foam isolator by thermo-dynamic transfer or simply put, vibration and heat.
Vibrations in the studio
When recording a voice or instrument in the studio, it is usually preferable to move the microphone away from the source so that the whole instrument is captured. For instance, the sound of an acoustic guitar comes from the sound hole, the spruce top, the pick on the strings and the combination of all of these as they combine in the nearby acoustic space. Placing the mic near the hole may be required on a live stage where the guitar is competing with other instruments and audience noise. In the studio, we have the luxury of moving the mic around until it sounds right. But as you move the microphone away from the guitar, you must increase the microphone’s sensitivity by increasing the gain. Not only does the microphone amplifier introduce noise, but other noises that may be masked when close mic’ing all of a sudden become apparent. This can be referred to as signal-to-noise. The further you are from the source, the lower the signal, and louder the noise.
Common noise problems include street noise from cars and trucks passing by; air conditioning or heating systems kicking in; foot stomping by the talent while they sign or play; paper sheets brushing as the musical score is turned to the next page; drums and bass vibrating through the floor… there is no end. This is precisely why top-end studios ‘float their floors’… to stop vibration borne noise.
|Studio Vocal Mic||Gain increased to capture nuances and deep low frequencies for warmth.||Usually mounted on a mic stand with a form of suspension. Not always sufficient. TriPad ads extra measure of isolation.|
|Studio Instrument Mic||Mic moved away from source to capture sound of instrument in the room. Sensitivity of mic increased, noise enters.||TriPad eliminates floor borne noise from transmitting through mic stand.|
|Drum Kit Overhead Mics||Stereo set of mics placed above drum kit captures vibrations from kick drum through the drum riser.||Eliminate resonance by adding TriPads to the overhead mic stands.|
|Electric Guitar & Bass Mics||Sound from amp resonates through the floor coupling with mic stand, causes comb filtering.||Isolating the mic stand reduces peaks and valleys from combining with instrument amp.|
Eliminating resonant frequencies
Up until now, we have been discussing noise. But noise does not just come in the form of background noise; it can also appear as a disruptive frequency known as resonance. For instance… when recording electric guitar, the sound from the speaker is generally captured using a nearby microphone. When the amp is playing, the speaker is moving back and forth which invariably will couple through the floor, the mic stand and into the microphone. As sound travels through these mediums, each will resonate at different frequencies. When these combine with the sound emanating from the loudspeaker, they will interact by either amplifying or canceling each other out depending on their phase and amplitude. This can ultimately cause a comb-filtering effect. Isolating the microphone stand helps eliminate the peaks and valleys for a more natural sound.
Managing resonance in a live sound environment
Studios are not alone in having to deal with noise and resonance. Live stages and orchestra pits also experience the same problems. In fact, stage resonance is a common problem that comes in many forms: Low frequency vibrations from the PA system will travel through the stage floor, through the mic stand and into the microphone competing with the desired sounds. Drum risers are usually hollow which means that they will have a resonant frequency of their own. The bass tones from the kick drum and bass guitar will cause the riser to vibrate, which in turn will resonate into the stand and drum mics. With bass guitar, the hollow stage can compete with the bass amplifier to create modes that can either cancel or amplify each other, causing strange peaks and valleys further disrupting the sound. The TriPad minimizes the problem by decoupling the microphone stand from the floor or stage and attenuating the problem resonant frequency from entering the mic.