In Part One we were introduced to the principJes by which perforated metals are able to serve particularly well in acoustical applications, particularly in noise control treatments.
In Part Two, we show how to use those concepts in a quantitative way, either to analyze an existing application or to design a new treatment in order to meet certain specified requirements.
II. The Transparency Approach
We begin with a closer look at the "Transparency Approach" in the use of perforated metals. We learned in Part One how to define a Transparency Index as an indicator of how easily sound can pass through a particular sample of perforated metal at high frequencies (see page 14). We now look at what this means in practice.
Subway station in Vienna; note the perforated metal facing for the sound absorptive ceiling treatment.