THE IMPULSE HAMMER MEASUREMENT

After many experiments with different measuring methods, the impulse hammer method finally became accepted worldwide. Here, the impulse hammer is struck on the top of one edge of the bridge and a miniature sensor (accelerometer) glued to the other side of the bridge with beeswax is used to record the vibrations of the body for all frequencies. One measurement takes about 1 second.

If this method is new to you: Don’t worry! The method is completely harmless, we ourselves have measured quite a few valuable Stradivaris, Guaneris and other valuable string instruments – the violins love it!

The advantage of this method is its speed and flexibility, the disadvantage is that the higher frequencies from 5 kHz upwards are relatively weakly represented in the spectrum. Therefore it makes sense to strike several times (5-10 times) in a row and calculate the average value from these measurements with a mouse click. This eliminates any blurring in the high frequency range.

THE TRANSFER FUNCTION – METHOD

Some luthiers prefer this method because it can better represent the influence of the cavity (Helmholtz) resonance. This method is also feasible with VIAS for Strings.

The instrument is excited at the bridge edge with a sine sweep using a shaker (or a steel pin vibrating in a magnetic field) and the radiated sound is recorded with a microphone and displayed as a frequency/amplitude curve.

Advantage: one can freely choose the frequency range and the duration of the sweep, the instrument emits a more or less well audible sound and the influence of the Helmholtz resonance is clearly visible.

Disadvantage: significantly higher technical expenditure and higher risk of incorrect measurements, the room influence comes into play and can only be somewhat mitigated by the use of a turntable. In addition, the “mass” of the shaker or the excitation unit influences the result in a mostly uncontrollable way. An extra amplifier is necessary for the shaker.

You are welcome to use this measurement method with VIAS, but we do not supply the necessary hardware. We discontinued this method in 2005 after several years.