Digital Noise Meter - Classification and Nature of Sound
(0) Very low frequency: 20-40Hz
(1) Low frequency: 40-80Hz
(2) Medium and low frequency: 80-160Hz
(3) Intermediate frequency: The span between 160Hz-1280Hz is the widest, almost all musical instruments and vocals are included, so it is the most important frequency band
(4) Medium and high frequency: 1280-2560Hz
(5) High frequency: 2560-5120Hz
(6) Very high frequency: 5120Hz-20000Hz
The theoretical audible range of the human ear is 20-20KHz. In the home high-quality preamplifier, the bass adjustment point is generally set at 80Hz.
The midrange adjustment point is generally set at 1Kz, and the treble adjustment point generally has three setting methods: 8KHz, 10KHz, 12KHz
The nature of sound, the physical quantity that describes sound
Sound is a pressure wave: when playing a musical instrument, tapping on a door, or knocking on a tabletop, their vibrations cause the medium—air molecules to vibrate rhythmically, causing the surrounding air to change in density and form a dense and alternating pattern. Longitudinal waves, which create sound waves, persist until the vibration dies away.
Sound is a kind of wave, and frequency and amplitude have become important attributes to describe the wave. The magnitude of the frequency corresponds to what we usually call pitch, and the amplitude affects the magnitude of the sound. Sound can be broken down into a superposition of sine waves of different frequencies and intensities. This transformation (or decomposition) process is called Fourier Transform.
Therefore, the general sound always contains a certain frequency range. The frequency range of sound that can be heard by the human ear is between 20 and 20,000 Hz. Waves above this range are called ultrasonic waves, while those below this range are called infrasonic waves. Animals such as dogs and bats can hear sounds up to 160,000 Hz. Whales and elephants can produce sounds in the frequency range of 15 to 35 Hz.
The propagation of sound is explained by quantum mechanics as the movement of atoms, forming sound waves. But this has no connection with terms like wave particles.
Loudness: The size of the sound (commonly known as the volume) that people perceive subjectively. It is determined by the "amplitude" (amplitude) and the distance between the person and the sound source. bigger. (unit: decibel dB)
Pitch: The pitch of the sound (treble, bass), determined by the "frequency". Infrasound, above 20000Hz is called ultrasonic) For example, low-end sounds or higher sounds such as thin strings.
Frequency is the number of sound waves that pass through a given point per second and is measured in Hertz, named after Heinrich Rudolf Hertz. This person sets up a table to demonstrate how frequency is related to cycles per second.
1 kilohertz or 1000 Hz means that there are 1000 cycles of sound waves passing a given point per second, 1 megahertz means 1,000,000 cycles per second, and so on.
Timbre: Also known as timbre, the waveform determines the timbre of the sound. The sound is different due to the characteristics of the material of the object. The timbre itself is an abstract thing, but the waveform is the intuitive expression of this abstraction. Different waveforms have different timbres. Different timbres can be distinguished through waveforms.
Tone: A regular, pleasant sound. Noise: From the point of view of physics, the sound emitted by the sounding body when it vibrates irregularly; from the point of view of environmental protection, any sound that interferes with people's normal work, study and rest, and that interferes with the sound that people want to listen to sound.
Pitch, loudness, and timbre are the three main characteristics of musical tones, and people distinguish sounds based on them.
When two objects collide and vibrate to produce sound, if the vibration frequency ratio of the two objects is an irreducible complex ratio, such as: 201:388, then we will find the sound harsh when we distinguish it; on the contrary, if the vibration frequency ratio of the two objects is A simple ratio that can be simplified, such as: 3:7, then we will find it very pleasant to distinguish. (discovered by Pythagoras)
