Acoustic characterisation of string instruments by internal cavity measurements

Area of Science:

• Acoustics
• Musical Instrument Science
• Vibrational Analysis

Background:

• Characterizing the acoustic properties of hollow-bodied string instruments is crucial for understanding their sound production.
• Traditional methods may be complex or costly, limiting accessibility for luthiers and researchers.

Purpose of the Study:

• To describe a method for characterizing the acoustic properties of hollow-bodied string instruments using internal cavity sound measurements.
• To demonstrate the utility of this method as a practical tool for instrument makers and researchers.

Main Methods:

• Utilizing inexpensive sub-miniature electret microphones to measure internal and radiated sound, as well as bridge admittance.
• Employing an impact hammer to excite body shell vibrations and internal cavity resonances.
• Analyzing the correlation between excited body vibrations, internal cavity resonances, and radiated sound spectrum.

Main Results:

• Internal cavity resonances are strongly excited by body shell vibrations.
• These resonances show a significant correlation with radiated sound, especially below 1.5 kHz in violins.
• The method effectively characterizes acoustic properties across the violin family (violin, viola, cello, double bass).

Conclusions:

• Internal cavity sound measurements offer a valuable, accessible technique for assessing string instrument acoustics.
• This approach provides practical insights for instrument construction and research.
• The findings are applicable to a wide range of hollow-bodied string instruments.