How I calibrated my contact microphone
Introduction I used the Hsu-Nielson method to find the frequency response of my contact microphones. This method involves cracking a mechanical pencil graphite on the microphone transducer. The microphone in question is the one shown above, and described in detail here: http://michaelkrzyzaniak.com/marshmallow.php I specifically used the white, low-gain variant. Experimental Setup and Results Figure 1: The mechanical pencil used in this experiment, with 0.5mm number-2 graphite Figure 2: Three millimeters of graphite were extended from the pencil Figure 3: Audio interface used for experiment (Scarlett 2i4), showing the settings used. Figure 4: Video showing the graphite being cracked. A small amount of putty was used to prevent the tip of the pencil tapping the transducer after the graphite breaks. The graphite is placed on the transducer and constant pressure is applied. When the graphite breaks, the pressure is released in a very short ti...