Analog Angle Blog

The sounds we create: Too much, too little, or just right?

Sounds are a classic analog phenomenon, and my newish car makes a lot of them. No, I don’t mean the normal ones of the engine running or the tires on the road. Instead, they are various beeps, chirps, warbles, chimes, and other sounds emitted to “warn” me, with ascending degrees of intensity, that something isn’t right or has changed. For instance, seat belt not fastened, hatch door open, following too closely at high speed, lane-keeping subsystem unable to see, CD still left in the player…you get the idea. I have identified those ones and there are at least a dozen or more that I haven’t figured out yet as they are the audio equivalent to the cryptic dashboard warning icons.

With all these icons, I sometimes feel as if I am trying to decode the aural equivalent of the Rosetta Stone while driving (Figure 1).

Figure 1 The Rosetta Stone, which contains the same decree in three symbolic representations, was a key to deciphering the Egyptian hieroglyphics, but the decoding still took decades. Source: Britannica

I checked online to see if a site catalogs all these sounds for my vehicle make and model to match them to the presumed cause. I didn’t find one, but I also realized that it wouldn’t have helped anyway. Many of the “alerts” are seemingly one-shot events that occurred at random times, so I could not record them and then re-play them to find the match. My other effort trying to describe it to the dealer was like a not-funny comedy sketch scene.

For a brief moment, I thought it might be a good idea if the warning or alarm condition was also spelled out in plain text on the car’s display, but that would add to distracted driving, of course. Having the vehicle actually speak—Your door is still open—would be anywhere from distracting to infuriating, so that approach wouldn’t work, either. It’s just one of those situations you learn to live with and move on.

It’s not just cars that have a catalog of alerts and sounds, of course. Medical instrumentation ranging from basic patient monitors to respirators and infusion pumps, all the way to operating-room equipment, have their own catalogs of sounds. The problem is that each vendor and each instrument had its songbook, so to speak, resulting in a cacophony of sounds that confused the medical staff.

It wasn’t always so, as you can see in the classic British murder-mystery movie Green for Danger, which takes place at a small rural hospital in 1943. It’s positively eerie as the operating and recovery rooms are silent, with no medical electronics at all.

There is such a variety of medical instrumentation sounds that it can result in confusion, misinterpretation, and audio overload. Medical professionals have developed the expected human response: they soon choose to ignore them all. Formal standards have been developed to remedy the problem to some extent, with the goals of standardizing the sounds across different products and from different vendors, also establishing a meaningful hierarchy of sound alerts from “nice to know” to “you should know” and finally “hey, this is life-threatening important.” Despite a fairly bland title, ISO/IEC 60601-1-8 “Medical electrical equipment – Part 1-8: General requirements for basic safety and essential performance” is the key standard for audio in this application niche.

At least these are sounds we can hear. There’s also a potential problem with ultrasound, those acoustic-energy sounds beyond the range of human hearing (about 20 kHz for children, less for adults). In addition to the use of ultrasonics as a diagnostic or investigative tool in controlled and bounded instrumentation, this energy is often intentionally used out in the open for alarms, motion detection, rodent repellents, sonar ranging, and as byproducts in regular operation of motors, railway cars, trucks, electronic oscillators and more. The availability of inexpensive, wide-range piezoelectric transducers makes it relatively easy to generate acoustic waves in the multi-megahertz range (Figure 2).

Figure 2 Ultrasound applications go far beyond the 20-kHz upper hearing range as some diagnostic and scientific instrumentation devices reach hundreds of MHz. Source: Olympus

An article in the December 2020 issue of Physics Today, “Ultrasound in air,” was especially interesting and somewhat worrisome. It discussed the issues, concerns, and unknowns of this topic. It included useful data on ultrasound sources, intensities, sensitivities, and relevant industry and government standards for exposure. The article also pointed out the many gaps in our knowledge of ultrasound ambient levels from various sources, as well as their likely dangerous thresholds. I had never really thought about all this pervasive ultrasound energy, whether created deliberately or unintentionally, nor about its impact.

Have you ever added extra, perhaps unnecessary sounds and alarm to a design even though they might confuse the user, just because it’s so easy to do? How do you personally deal with products which inundate you with excessive alerts and sounds that you can’t decode?

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