Do the physical characteristics make a big difference in tactile transducer output level and frequency response?
• Yes. Just like room modes, standing waves occur in solid objects such as wood and concrete. The size of an object, its density, its Young’s modulus, … all play a role in the vibrational modes of an object. The speed of sound in a solid object will also be much higher that it is in air. This increased velocity should have the effect of stretching the nodal frequency response as compared to the room’s modes in air, so that the low frequency response isn’t much affected, but instead the opposite has been witnessed. Frequency response of transducers in a couch will have far more severe peaks and nulls than is typically measured of subwoofers in normal walled rooms. Peaks and nulls in a couch will be multiples of octaves just like they are in room modes. Two nulls with extreme “suck out” separated an octave apart with a resonant peak directly in the middle is common. Combating this with layers of materials of different springiness and absorption coefficients is most likely possible and
