Noise has become a big issue in the modern world, causing problems such as poor concentration and noise-induced hearing loss. While there are many efforts to reduce noise, it’s not always best to eliminate it completely, especially when noise can be an important factor in evaluating the performance of a machine, it can be more effective to control it properly. Noise engineering is showing promise with research that focuses on making noise more pleasant to listen to rather than eliminating it.
In the modern world, noise has become the enemy of people. The noise generated by all kinds of machinery amongst the forest of buildings significantly reduces people’s ability to concentrate, and a hearing disorder called noise-induced hearing loss is now a common condition. In fact, many city dwellers suffer from severe noise pollution. As a result, efforts are being made to reduce noise by installing sound barriers around cities and enforcing noise regulations. But is removing noise from machines really the best way to go?
It’s safe to say that there’s hardly a home today that doesn’t have a refrigerator. The electric refrigerators we use today were developed in the 1920s by companies such as General Electric, founded by the famous Thomas Edison, and General Motors, which dominates the automotive market today. However, these early electric refrigerators were not only huge in size, but due to the lack of technology, the vibrations and noise were so severe that they couldn’t be installed indoors as they are today. Technological advancements have since shrunk their size and made them what they are today. They’re smaller, but they perform better, and they’re much quieter, so they don’t feel out of place indoors. What’s more, research is ongoing to develop a completely silent refrigerator. However, eliminating noise completely is not as good an idea as it sounds, according to acoustic engineers.
Noise engineering is the science of measuring “unpleasant sounds,” analyzing how they affect people, and studying ways to predict or suppress them. Noise engineering divides noise into two main categories. The first is aerodynamic noise, which is generated by waves caused by the collision of an object with air, and the second is structural noise, which is caused by mechanical vibrations that displace adjacent air. The noise we feel is usually a combination of the two, and the unpleasantness of the noise is determined by the intensity and frequency of the sound. If the noise is not very loud, it can be solved by using soundproof covers. However, when the noise reaches the size of a car engine, it becomes difficult to muffle it, and the vibration between the engine and the cover can cause even more noise. Therefore, the best way to reduce noise is to adjust the frequency. When a waveform formed at one frequency meets a waveform with the opposite phase, it cancels out, and the method of reducing noise using this principle is called active noise control. In theory, this method can completely eliminate noise. In practice, however, it is difficult to pinpoint the noise waveforms that multiple noise sources create simultaneously at different locations. Because a different design is required for each noise waveform, it is not possible to cancel all noise with current technology.
Noise engineering initially focused on suppressing noise completely. However, in the face of the difficulties described above, research has shifted to improving the audibility of noise rather than eliminating it. Experiments on the relationship between noise and human psychology have been a major influence on this change of direction.
Currently, most machines produce noise, which is both repulsive to people and a measure of machine performance. For example, if a vacuum cleaner were completely silent, it would appeal to people because it would clean in silence, but people tend to feel that a vacuum cleaner that makes some noise performs better. A classic example is the sound of a car engine. Manufacturers of supercars, or high-end performance cars, take great care with the sound of their engines. They routinely develop their own engine sounds and patent them. One of the leading supercar companies, Italy’s Maserati, is so focused on sound that it invites symphony conductors to help research its engines. According to Wired, an American magazine that studies the impact of technology on society, people get excited when they hear a supercar engine, especially women. This supports the argument that people perceive engine sound as a measure of performance.
As we’ve seen, noise is a big problem in the modern world. However, noise engineering research has shown that eliminating noise is not the only solution. Some people prefer the quietness of a luxury sedan, while others love the roar of a supercar engine. Advances in noise engineering have made it possible to design for different noise needs. If we can create different sounds in the same car engine, we can extend that to entire machines. Today’s machines have a wide range of applications, from automotive to construction to home appliances, and they come in many different types. There is no end to what acoustic engineering can and will do in the future.
