Love the sound of music? The ability to hear is a unique gift that allows us (well, most of us) to differentiate a wide variety of sounds, including music, speech, motion and even – ironically – silence.
There are good and bad sounds, loud sounds and soft sounds, as well as sounds that are meant to bring calm or raise alarm. But there are also inaudible sounds, which, apart from in scientific circles, are not really talked about, simply because they are not able to be heard, at least not by the general population.
There are two types of inaudible sounds. There are those sounds that are too low for the human hearing mechanism to pick up. They fall below the threshold of 20 hertz (Hz - the unit of frequency) and are therefore called infrasonic sound waves. On the other end of the spectrum are ultrasonic sounds, which is what we’ll be explaining in this post.
What are ultrasonic sounds?
The highest sound frequency the human ear can detect is 20,000 kilohertz (KHz). An ultrasonic sound wave is one that breaches this upper limit of the audible range, vibrating at more than 20,000 beats per second. However, that’s for the average healthy human ear. There is a school of thought that there are a small fraction of people, including babies, young people, and adult women, who can sense these sounds, often causing discomfort. In fact, according to this Live Science article about ultrasonic waves, people affected by ultrasonic sounds may be led to think they are crazy since others around them might not be able to hear them.
Generally, as you get older, the upper limit of your audible range will likely decrease. For example, a 50-year-old man or woman with healthy hearing will probably not be able to hear sounds vibrating at a frequency of more than 15 KHz. But even among older folks, there is a small fraction of the population who are believed to have rather acute hearing and who can still detect ultrasonic sounds.
When it comes on to losing hearing, factors such as listening to loud music, continuously working in a noisy environment, or working with sounds (such as audio engineering), can also cause damage to your ears and lower your audible range. That’s a subtle way of saying that, as musicians, you should try not to expose your ears to loud music on a continuous basis. This might be difficult to get away from, especially if you're an artist or session musician, who spends a lot of time around sound in the studio or on stage, but there are implements such as earplugs that can help to protect your hearing.
With that said, is ultrasonic sound safe?
Currently, there is a lot of research going on to find out whether inaudible sounds, that is both infrasonic and ultrasonic, have any harmful effects on humans. There is a school of thought that the infrasonic sound generated by wind turbines, for instance, can have a negative impact on humans who live close by. There have also been devices developed where ultrasonic waves are used to ward off young people, as well as ones used by teens to create ultrasonic ringtones only they could hear.
However, no clear link has yet been forged between inaudible sounds and human effect. Research such as this article on inaudible sound is still wrapped up with determining how humans actually perceive sound, let alone how an inaudible sound affects us, and what intensity (if any effect at all), etc.
The main fact that is known is that ultrasound is a common part of daily life. For one, ultrasound is commonly used in the medical field to carry out imaging procedures and for treatment of some ailments. Also, because other animals are able to hear sounds that are ultrasonic to humans, devices exist that are used to interact with them. For example, police personnel use whistles that are capable of outputting sounds above the audible range in order to communicate with dogs. Also, the pest control community have created various devices that are said to only be audible to rats and other rodents in order to keep them away. On top of that, ultrasonic waves are used in the cleaning of brass musical instruments, plus they are produced naturally by various machines and other objects in daily life.
By the way, in the music community, while it would be pointless to make inaudible music, there have been musicians who seemed to have been attracted to ultrasonic sounds – at least in name. A band from Scotland called themselves Ultra-Sonic and made a career out of hardcore techno music during the 1990s and 2000s. Ultrasound, on the other hand, is an English indie band that performs in the genres Britpop and Alternative Rock.
So, there you have it, a brief explanation of ultrasonic waves. We hope you found it interesting. Have you ever been affected by ultrasonic waves?