From the Archives: The Past Quarter Century

by Eric E. Ungar

The editor of NNI has invited me to reflect on what has changed over the last 25 years, noting that I was mentioned in the 1993 issue of NNI, a quarter century ago. That is not an easy task for someone like me, who thinks of everything in the past as “yesterday” and who has been in the acoustics/vibration field for almost 60 years. Nevertheless, here are my views, based predominantly on my experience and undoubtedly on my prejudices.


About 25 years ago, US government entities that had sponsored advancements in intellectual tools, such as statistical energy analysis (SEA),[1] began changing their focus to supporting projects aimed at hardware development. Thus, research organizations outside of academia also switched to hardware-related projects and to industrial consulting work, causing many of their employees to move to jobs in industrial firms. As a result, such firms have developed greater acoustics capabilities and better information relating to the acoustical and vibration aspects of their products.

In the past few decades, such government entities as the Environmental Protection Agency, the Federal Transit Administration, and the Occupational Health and Safety Administration promulgated regulations and sponsored investigations related to the control of vibration and noise; it is my perception that they have more recently been relatively inactive in our field. However, many communities have picked up the ball and promulgated noise ordinances of various levels of complexity. In recent years the idea of “soundscapes”—the environmental acoustics analog to landscapes—has obtained some traction, but it has not yet found widespread application.

It is no surprise that the increased use of computers and networks has had a great effect on us in the noise and vibration community, as on so many others. Many program packages, some based on finite-element methods, have become available for the prediction and analysis of noise and vibration information, enabling practitioners to obtain results relatively quickly and inexpensively.[2] Of course, we all have become avid users of personal computers for computation, word processing, and for finding and storing information. The perception that everything can be found online has virtually made reference books obsolete, particularly in the minds of younger practitioners.[3]

The burgeoning demand for computer components and the like has led to the construction of a considerable number of facilities for the production of microelectronics and other high-technology devices and also for nanotechnology research. These facilities typically require extremely benign noise and vibration environments and have given rise to industries and specialty consultants that provide guidance and equipment aimed at achieving these environments.

The increased availability of microelectronic components for transduction and data processing in the recent decades has led to vast practical improvements in our ability to acquire data. Measurements that used to require the use of heavy and bulky instruments now can be done by means of equipment that fits into a shoebox or even into a shirt pocket. The newer instrumentation has greater analysis and recording capability, with some including features for remote monitoring. Widespread Wi-Fi and cell coverage has enabled the remote performance of long-term measurements, observation of results, adjustments of the instruments, and the downloading of data—all without a person at the measurement site. As a result there has been increased demand for more data and more sophisticated data analysis.[4] The resulting greater amount of data, requiring increased data storage, also has put pressure on our networks and servers.

The advanced instrumentation and computation means have given rise to so-called active control systems for counteracting unwanted sound and vibration. Much theoretical work was done early on and has more recently led to the commercial availability of consumer items like “noise-cancelling” headphones and industrial equipment like vibration isolation platforms that vastly reduce the vibrations transmitted from facility floors to electron microscopes and the like. The aforementioned means have also led to the development of “auralization” systems—arrangements that enable one to hear the acoustics expected in a space, such as a concert hall or classroom that may exist only on paper—enabling one to understand the acoustics better than one could from data plots and charts.


It has been an interesting time. I wonder what the next 25 years will bring!

[1] SEA in essence was the brainchild of Richard Lyon, whose company was described in the 1993 issue immediately after the article that referred to me and who passed away at the beginning of 2019.

[2] But the accessibility of such programs has made it possible for users without a good understanding of the underlying science to arrive at computed predictions and evaluations without being able to judge whether their results make much practical sense.

[3] This is especially true of physics and engineering handbooks, and even of compilations such as the 1997 Encyclopedia of Acoustics and the 2007 Handbook of Noise and Vibration Control, both edited by Malcolm Crocker. I have been unable to find takers for many books I have been trying to give away as I contemplate retirement.

[4] I often wonder how much of the data we take is really useful and whether those who demanded the measurements understand what all the data mean.