Noise is any unwanted sound that causes discomfort, irritation, or disrupts communication, work, study, or rest.
Hearing range of the human ear: 20Hz–20kHz
Most sensitive range: 2kHz–5kHz
Comfortable volume: 0–40dB
Uncomfortable threshold: 60dB+
Risk of hearing loss: 120dB+ (even one minute can cause temporary deafness)
Types of Noise by Frequency
Low-frequency noise (20–500Hz): air conditioners, trains, airplanes, car engines, ships, washing machines, refrigerators.
Travels long distances, penetrates walls easily, causes the most harm.
Mid-frequency noise (500Hz–2kHz): elevators, traffic sounds.
High-frequency noise (2kHz–20kHz): horns, instruments, dogs barking, loudspeakers, conversations.
Weaken quickly over distance, easier to block.