The sounds of four notes struck at 3 velocity strikes, was produced by the calibrated electronic striker used in the string vibration tests in chapter 2.The table below illustrates how each sound is coded, denoting the durations in seconds (s). The notes were sounded un-damped till the sound died out, so their durations (s) were measured by the longest sounding of the note. The faster the velocity strike (v), results in a louder and longer note and notes with a lower frequency (Hz), will have a longer duration. Start times of the each sound were equalised using Pro Tools 10, for an equal measure of rates of decay and attack. 20 Hz and below was filtered out by a high pass filter in Pro Tools 10, to help eliminate extra low frequency room noise. The key numbers are different because the STU pianos have 97 keys and the STE piano has 88 keys.

DPA 406 omni microphones, each calibrated at 94dB, were positioned around the pianos at equal angles and distance of 3 or 6 metres from a designated point on each piano frame and cabinet, to create the sound fields.The microphone arrays were used to pinpoint the directivity of the piano sound. The direction of the radiated sound from the piano was noticeably different in the two pianos and therefore was considered to be a consequence of design differences, such as string coupling, soundboard thickness and rib shape, soundboard wood type, length, mass and tension of the strings. A sound level metre, Virtual Sound Level Meter (VSLM) ²¹⁸ was used to measure the peak amplitude sound level (volume) at the beginning of the note, and an averaged amplitude sound level over the complete duration of the note. Software using FFT technology, Fuzz measure 3 Pro,²¹⁹ was used to filter the whole note duration into smaller duration periods, to examined the attack and decay transients of the sound.

The recording equipment and the audio engineer were the same for the recording of each piano sound.A Focuscrite preamp was calibrated at -10 Omni pre amp calibration and a Fire Face UFX interface was used with recording software Pro Tools 10, designating one microphone to one channel, i.e. track 1 corresponding to microphone 1. Each microphone (mic) was positioned at a height of 1.5metres. A sound level meter (SLM)microphone was positioned in the piano to record the sound level of the hammer strike 10cm above the striking point of the string.

²¹⁸ Virtual Sound Level Meter: MATLAB Based Software, 2016, Sourgeforge, http://sourceforge.net/projects/vslm
²¹⁹ FuzzMeasure software: http://supermegaultragroovy.com/products/fuzzmeasure/