21 March 2011

Review: Jürgen Meyer: Akustik der Gitarre in Einzeldarstellungen

Theory as basis for guitar construction

The systematic discussion about materials which are used when constructing guitars is mandatory.  When you want to dig in further and try to understand the sound capabilities of a guitar you need to have a basic understanding of mathematics and physics. One of the prominent authors in this domain is Jürgen Meyer. He dedicated his work to all aspects of acoustic research. His knowledge about musical acoustics is not strictly theoretical. He always breakes down the problems to a practical level, so that his scientific findings can be reproduced or used as a starting point for further development.

In his book „Akustik der Gitarre“ he focuses his analyses on the guitar. You will find a selection of articles dealing with:

  • The sound of the guitar
  • The tuning of the deep fundamental resonance
  • Resonance characteristics in middle frequencies
  • A Hearing test to evaluate the sound quality
  • Definition of quality criteria
  • The relationship between sound quality and construction
  • Bibliography
In the chapter about the sound of the guitar you will find an analytical description of the overall sound. This will be broken down to the influences of the instrument, playing technique, sound radiation and recording engineering. All articels are as in the whole book accompanied by detailed charts and pictures. In this chapter he analyses e.g. guitars from Hauser, Ramirez and Örökenyi.

The second chapter, for me one of the most important ones, deals with measurement methods used, fundamental frequencies, cavity resonances and frequencies of soundboard and back. Of course the influence of  the bracing system is also included. The graphs and curves presented speak for themselves. So that the German text should be with a little effort understandable.

In his statements to the response of the guitar in middle frequencies he introduces Chladni figures and 3D-modelling of the movement of the plates. You will get in impression how complex the movement of  the soundboard is in reality. It is surely not a stiff membrane. Of course the coupling of plates and resonances is described and discussed.

The result of the hearing test, which was done with a variety of guitars, music and persons, was a catalog of subjective acceptance criteria which could be matched to sound quality and measurable data of acoustical properties.

The definition of quality criteria was derived from the objectiv measurements from the sound characteristics and the results from the hearing tests. He found 19 criteria (numerical data) which could be derived from the frequency measurements. If  you measure a new guitar and get these appropriate data, you can clearly see whether the instrument will be above or below the average. 

In the last chapter you will find a round-up of the results. He takes his 19 citeria and correlates them to the constructional part of the guitar. There is a discussion of different bracing systems and their influence to sound quality. Further topics covered in relation to sound quality are:
  • Soundboard
  • Bridges (form and weight) 
  • Ribs (high)
  • Soundhole
  • Tonewood

Putting things together this book confirms that the pragmatic and empirical approach which luthiers took the last 150 years was suitable to reach the quality of sound in modern guitars. For me it was my first book about acoustics of the guitar and a starting point for further reading. I still use it today to get to the important points of construction. The results of the book was the basis for further developments of high volume production of guitars. (Not my main interest ;-)

Ongoing reading: Left-Brain Lutherie by David C. Hurd which will be covered in a future review.

Jürgen Meyer:
Akustik der Gitarre in Einzeldarstellungen
Bochinsky 1985, ISBN 3-923639-66-X

Stay Tuned!