Have you ever been conversing with someone on a station platform when the sound of a passing train makes it difficult to hear their voice? This phenomenon is called "masking" when one sound is made harder to hear by another sound, or is completely lost.
In this trivia, we will explain the masking phenomenon as clearly as possible, using everyday examples.
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Tomoyasu Takaoka
Basic knowledge of masking
How sound is "heard
Our ears recognize sound and transmit it to the brain through the following processes.
- Sound first passes through the ear canal and vibrates the eardrum.
- Vibrations from the eardrum are transmitted through the three bones in the middle ear (ossicles) to the cochlea in the inner ear.
- For each frequency of sound (pitch of sound), the hair cells in the cochlea respond.
- The hair cells convert sound vibrations into electrical signals, which are delivered to the brain via nerves and recognized as sound.
What is the masking phenomenon?
When multiple sounds are heard at the same time,Phenomenon in which loud sounds mask small sounds and make them harder to hearoccurs. This ismasking phenomenon.
Hidden sound.muskieThe sound of concealment.maskerWe call it "the
When the masker is large, the response of the hair cells becomes saturated and less responsive to the masky. This makes it difficult to hear small musky sounds.
Familiar examples of masking
When listening to music in a quiet room, you can hear it well even at a low volume.
However, in noisy places such as on a train or in the city, it is difficult to hear unless the volume is turned up.
This is because ambient noise (masker) makes the ear less responsive to music (masky).
In general, the louder the masker, the louder the masking required to be heard.
This phenomenon, in which the volume required to hear the masky is increased, is called the masking phenomenon.
Masking complexity
There are many factors other than the size of the masker or mask key that determine how much intensity (degree of masking) of the masking phenomenon occurs. Typical factors are listed below.
Factors affecting the amount of masking
Frequency (pitch of sound)
The closer the frequencies of the masker and mask key are, the greater the amount of masking.
However, even when the frequencies are far apart, higher tones are less likely to mask lower tones, but lower tones are more likely to mask higher tones. This is calledfrequency responseIt is called "the
Timing of sound (time displacement)
The amount of masking is greatest when the masker and masky sound at the same time. However, if the masker occurs before the masky and stops, or vice versa, the amount of masking will still occur, although it will be less. This is calledtime characteristicIt is called "the
Sound direction and spatial arrangement
The amount of masking depends on where the sound is coming from. If the masker and the mask key come from the same direction, the amount of masking will be greater. The amount of masking is also reduced when the masker and masky come from different directions. This is calledSpatial CharacteristicsIt is called "the
In the case of language, there are other effects besides masking.
When we hear sounds, our brain processes the sounds that come in through our ears. When sounds have meaning, "guesses" based on familiar words and experiences may come into play.
- Conversations in one's native language can be heard relatively well, even in somewhat noisy environments.
- A foreign language that you are not accustomed to hearing is more difficult to understand in the same environment.
This is due to the influence of verbal information stored in the brain and past listening experiences.
summary
The phenomenon of masking occurs in many aspects of our daily lives. Although it is a nuisance that interferes with our hearing, it can help us control the sound environment if we make good use of it. For example, playing moderate ambient music in an open office so that people are not disturbed by outside sounds and thus improve work efficiency, or daring to play music in front of the door of a hospital examination room to protect conversations between doctors and patients who do not want to be heard, are examples of the application of the masking phenomenon.
In recent years, with the development of acoustic equipment and the trend toward respecting personal privacy, the understanding and use of masking phenomena has become even more important, and knowledge of masking is being used in various fields.