Figure 1. A.

Diagram of experimental setup for investigation of airborne sound-induced substrate vibrations in a pine stick, not shown to scale. The accelerometer was screwed into the stick and the laser beam was focussed on a grass sphere nearby. B. Graph of the acceleration of induced substrate vibrations during broadcast stimulation of the stick with pure sine wave tones from a loudspeaker of 80 dB SPL intensity; at 7 kHz three sound intensities were tested. C. Graph of the vibration spectrum induced in the pine stick by a 7 kHz airborne sound broadcast at 80 dB SPL, as recorded by a laser vibrometer. Velocity: 20*log (X mms⁻¹/90 mms⁻¹) [dB]