Page 89 - Fall2021

Letters to the Editor
Acoustics Today welcomes “Letters to the Editor.” Letters (maximum 150 words) can be on any topic related to acous- tics or any comments on material in recent issues of Acoustics Today. Letters will be published on a space-available basis. Letters should be sent to apopper@umd.edu.
The Least Useful Equation in Acoustics?
It is always disconcerting to see the inflated importance that acousticians assign to the wave equation, as well as their failure to comprehend its meaning. Dr. Eastland’s fine article in the Spring 2021 issue of Acoustics Today (https://bit.ly/3ukKcKK) provides a clear example of this problem. He correctly states that “The [wave] equation relates the temporal and spatial changes to these variables,” but the previous sentence incorrectly claims that the “[wave] equation provides the mathematical relationships between the variables of interest in acoustics, often the acoustic pres- sure or particle velocity and the speed of the wave.”
Three first-order differential equations that determine “the mathematical relationships between the variables of inter- est.” Pressure and density are related by the equation of state, pressure and velocity are related by the momentum equation (e.g., the non-dissipative Euler equation), and density and velocity are related by the continuity equation. That content of those local relations is obliterated when they are com- bined to form the global second-order wave equation.
Steven L. Garrett
sxg185@psu.edu
Pine Grove Mills, PA 16801, USA
Letter to the Editor
The article Computational Methods and Techniques Across Acoustics by G. C. Eastland in the Spring 2021 issue of Acoustics Today (https://bit.ly/3ukKcKK) talked
about the role of computers in acoustics. Analysis con- cepts based on energy principles developed by W. P. Mason might also be added to the list due to their impor- tance in entire industries, including the entire sound reproduction industry, every ultrasonic device employing piezo electric material, and every active or passive sonar
device. The technique allowed a designer to re-configure an acoustic device into an electrical circuit analogue and from there develop its acoustic and electrical properties.
Dr. Mason was the president of the Acoustical Society of America (ASA) in 1956, was an ASA Gold Medalist, and the author or co-author of numerous publications.
Bruce Keller
bdkeller4@adelphia.net
The Journal of the Acoustical Society of America
JASA Call
For Submissions:
JASA is currently accepting manuscripts for the following Special Issues:
• COVID-19 Pandemic Acoustic Effects
• Education in Acoustics
• Noise-Induced Hearing Disorders: Clinical and Investigational Tools
• Reconsidering Classic Ideas in Speech Communication
Special Issue articles are free to read for one year after publication and don’t incur any mandatory page charges.
Find out more at
asa.scitation.org/jas/info/specialissues
Fall 2021 • Acoustics Today 89