This blog post examines how noise affects modern life and whether noise reduction is always the optimal approach.
In modern society, noise has become the enemy of people. The noise generated by all kinds of machinery amidst the forest of buildings significantly reduces people’s concentration, and noise-induced hearing loss is now a common condition. In fact, many urban residents suffer from severe living noise. Therefore, various efforts are being made to reduce noise, such as installing sound barriers throughout cities and strengthening noise regulations. But is eliminating noise from machines truly the best solution?
It’s no exaggeration to say that almost every household today uses a refrigerator. The electric refrigerators we use today were developed in the 1920s by companies like General Electric, founded by the renowned Thomas Edison, and General Motors, which currently dominates the automotive market. However, early electric refrigerators were not only enormous in size but also suffered from severe vibration and noise due to technological limitations, making indoor installation impossible at the time. Through subsequent technological advancements, their size was reduced to achieve their current form. While smaller, their performance improved significantly, and noise levels decreased markedly, allowing them to be installed indoors without any sense of incongruity. Moreover, research to develop completely silent refrigerators is steadily progressing. However, noise engineering experts explain that completely eliminating noise isn’t necessarily as beneficial as one might think.
Noise engineering is the field that measures ‘unpleasant sounds’, analyzes their impact on people, and studies methods to predict or suppress noise generation. Noise engineering broadly categorizes noise into two types. The first is aerodynamic noise, generated by waves created when objects collide with air. The second is structural noise, produced when mechanical vibrations cause adjacent air to vibrate. The noise we perceive is generally a combination of these two types, and the unpleasantness of noise is determined by its intensity and frequency. When noise levels are low, noise-reducing covers can be used as a solution. However, when noise reaches the level of a car engine, noise reduction becomes difficult, and vibrations between the engine and the cover can actually generate even louder noise. Therefore, the best way to reduce noise is to adjust its frequency. When a waveform formed at one frequency encounters a waveform with opposite phase, they cancel each other out. The method of reducing noise using this principle is called active noise control. Theoretically, this method can completely eliminate noise. However, in reality, it is difficult to precisely identify the noise waveforms produced simultaneously by multiple noise sources at different locations. Since different designs are required for each noise waveform, current technology cannot completely cancel all noise.
Noise engineering initially pursued research aimed at completely suppressing noise. However, faced with the aforementioned difficulties, the focus shifted from eliminating noise to improving it to a more pleasant level. This shift was significantly influenced by experiments examining the relationship between noise and human psychology.
Most modern machines generate noise, which can be bothersome to people while also serving as a measure of machine performance. For instance, while a vacuum cleaner that operates completely silently might attract attention by enabling cleaning in a quiet environment, people tend to perceive vacuum cleaners that produce some noise as having better performance. A prime example is the sound of a car engine. Supercar manufacturers, those boasting the highest-end performance, pay particular attention to engine sound. They develop their own unique engine sounds daily, and every sound developed is promptly patented. One of the leading supercar companies, Italy’s Maserati, places such emphasis on sound that it even invited a symphony conductor to participate in engine research. According to Wired, an American magazine that studies the impact of technology on society, people become excited when they hear supercar engine sounds, with women showing particularly higher levels of excitement. This supports the claim that people perceive engine sound as a measure of performance.
As previously discussed, noise poses significant problems in modern society. However, noise engineering research has revealed that eliminating noise is not the only solution. Of course, preferences vary: some may favor the quiet refinement of a luxury sedan, while others enjoy the thunderous roar of a supercar engine. Advances in noise engineering enable designs tailored to diverse noise requirements. If different sounds can be produced from the same car engine, this capability can be extended to the entire machine. Today, machinery is applied extremely widely, from automobiles and construction to home appliances, and its types are diverse. The tasks noise engineering can undertake and the possibilities it holds are boundless.
