Some empirical observations on sound level properties of recorded piano tones

Preliminary to an attempt at measuring the relative intensities of overlapping tones in acoustically recorded piano music, this study investigated whether the relative peak sound levels of recorded piano tones can be reliably inferred from the levels of their two lowest harmonics, measured in the spectrum near tone onset. Acoustic recordings of single tones were obtained from two computer-controlled mechanical pianos, one upright (Yamaha MX100A Disclavier) and one concert grand (Bösendorfer 290SE), at a range of pitches and hammer velocities. Electronic recordings from a digital piano (Roland RD250S), which were free of mechanical and sound transmission factors, were included for comparison. It was found that, on all three instruments, the levels of the lowest two harmonics (in dB) near tone onset generally increased linearly with the peak root-mean-square (rms) level (in dB) as hammer velocity was varied for any given pitch. The slope of this linear function was fairly constant across midrange pitches (C2 to C6) for the first harmonic (the fundamental), but increased with pitch for the second harmonic. However, there were two sources of unpredictable variability: On the two mechanical pianos, peak rms level varied considerably across pitches, even though the strings were struck at nominally equal hammer velocities; this was probably due to the combined effects of unevenness in hammer-string interaction, soundboard response, and room acoustics. Moreover, for different pitches at equal peak rms levels, the levels of the two lowest harmonics varied substantially, even on the electronic instrument.(ABSTRACT TRUNCATED AT 250 WORDS)