Physics knowledge of acoustic phenomena, seeking to share the knowledge points of physics acoustic

Chapter 1 Acoustic Phenomena.

Relationship between tone and frequency: The higher the frequency, the higher the tone.

Relationship between loudness and amplitude: The greater the amplitude, the greater the loudness.

Characteristics of sound. Timbre: The sound emitter is different, the timbre is different, and the timbre is related to the material and structure of the sound emitter.

Knowledge must be memorized in the secondary school entrance examination.

Must-remember 1: Tone.

1.Pitch refers to the pitch of the sound.

2.Frequency refers to the number of times an object vibrates per second, it is a physical quantity that describes how fast or slow an object vibrates, and frequency determines the tone of sound.

3.The frequency range that causes human hearing is 20 Hz 20 000 Hz 4Ultrasound: frequencies higher than 20 000Hz

5.Infrasound: Sound with a frequency below 20Hz.

Must-remember 2: Loudness.

1.Loudness refers to the magnitude of the sound.

2.Amplitude is a physical quantity that describes the amplitude of an object's vibration.

3.The greater the amplitude of the object, the louder it is, and the loudness is also related to the distance from the emitter.

MUST-NOTE 3: Timbre.

1.We can tell different sounds even if they have the same pitch and loudness, because they have different timbres.

2.The structure and material of different sound emitters are different, and the timbre of the sound produced by them is also different. The vocal body can be distributed according to the timbre.

Admission and promotion of test centers.

Test point 1: One of the characteristics of sound – tone (emphasis).

Test point 2: Characteristics of sound 2 - loudness (emphasis).

Test point 3: Characteristics of sound 3 - timbre (emphasis).

Tenor Soprano refers to a high pitch.

And "deafening" means loud.

The pitch is mainly determined by the frequency of the sound. The pitch rises and falls with the rise and fall of the frequency. The timbre is determined by the material and structure of the articulated body. Even if the tone is the same, we can also hear different articulation bodies because of their different timbres.

You can use the piano and the erhu to play the same piece of music with the same voice, and the two have the same tone, but people can easily distinguish the piano sound and the erhu sound, which is the difference in timbre between the two, and the difference in timbre is determined by the structure and material of the sound emitter, and no matter how much the piano plays, it cannot play the timbre of the erhu.

Such as mezzo-soprano and soprano:

The characteristic of the sound you hear is that when you say good or not, it refers to the timbre.

The high and low of the voice refers to the pitch, which is related to the frequency of vibration of the vocal cords.

The pitch is generally determined by the main frequency of the sound frequency, and the higher the frequency, the higher the pitch.

Timbre is determined by the number of frequencies that the sound contains and their relative strength to each other, in terms of the "spectrum" of the sound.

For example, a percussion instrument, a big gong, has a very rich vibration pattern, resulting in a sound containing so many frequencies that it sounds like noise.

The common tenor soprano refers to a high pitch.

And "deafening" means loud.

In fact, you only need to identify the conditions given to you in the previous question to determine whether the pitch is high or loud.

Pitch refers to the frequency of sound, and timbre is determined by the characteristics of the object.

1 .Occurrence of sound: Produced by the vibration of an object. The vibrations stopped, and so did the vocalizations.

2.Propagation of sound: Sound is transmitted by medium. Vacuum cannot transmit sound. Usually the sounds we hear come from the air.

3.Speed of sound: The speed of propagation in the air is: 340 m sec. Sound travels faster in solids than liquids, and in liquids it travels faster than in air.

4.The measurable distance with echo is s=1 2vt

5.There are three characteristics of a musical sound: pitch, loudness, and timbre. (1) Tone: refers to the height of the sound, which is related to the frequency of the emitter. (2) Loudness: refers to the magnitude of the sound, which is related to the amplitude of the emitter and the distance between the sound source and the listener.

6.Ways to reduce noise: (1) attenuation at the sound source; (2) weakened during propagation; (3) Weakened in the human ear.

7.Audible sound: sound waves with frequencies between 20Hz and 20190Hz: Ultrasound: sound waves with frequencies higher than 20190Hz; Infrasound: Sound waves with frequencies below 20Hz.

8.Ultrasonic characteristics: good directionality, strong penetrating ability, and concentrated sound energy. Specific applications include: sonar, B-ultrasound, ultrasonic velocity tester, ultrasonic cleaner, ultrasonic welder, etc.

9.Infrasound waves: they can travel long distances, easily bypass obstacles, and are pervasive.

Infrasound waves of a certain intensity will cause harm to the human body, and even destroy machinery and buildings. It is mainly produced in volcanic eruptions, tsunamis, etc. in nature, and infrasound waves can also be generated by human-made rocket launches, airplane flights, train and car Mercedes-Benz, and nuclear **.

The physical knowledge points of acoustic phenomena are as follows:

1. Sound generation and propagation.

1. Sound generation: Sound is generated by the vibration of objects; Everything that makes sound vibrates, vibration stops, sound stops.

2. Sound propagation: The propagation of sound requires a medium (the substance that transmits sound is called a medium), and vacuum cannot transmit sound. Solids, liquids, and gases can all transmit sound.

3. Sound waves: The vibration of the sound emitter will cause the density of the air to change and produce sound waves.

4. Speed of sound: the speed of sound propagation.

5. Factors that determine the speed of sound: the type of medium and the temperature of the medium. 15 The propagation velocity of sound in the air is 340m s.

2. How we hear voices.

1. The structure of the human ear: outer ear, middle ear, inner ear.

2. The process of perceiving sound: the vibration of the sound source produces the propagation of sound, air and other media, and the vibration of the tympanic membrane. (Sounds from the outside cause the eardrum to vibrate, and this vibration is transmitted through the ossicles and other tissues to the auditory nerve, which transmits signals to the brain so that the person hears the sound.)

3. Bone conduction: sound can also be transmitted to the auditory nerve through the skull and jaw, causing hearing, and this conduction mode of sound is called bone conduction.

4. Binaural effect: the distance from the sound source to the two ears is generally different, and the time, strength and other characteristics of the sound to the two ears are also different, and these differences are an important basis for judging the direction of the sound source, which is the binaural effect.

1. Sound is produced due to the vibration of the object, and the vibration stops when the sound stops.

2. The object that is emitting sound is called the sound source, and solids, liquids, and gases can all be used as sound sources.

3. Sound can propagate in solids, liquids and gases, but not in a vacuum; The substance that is capable of transmitting sound is called a medium; The sounds we usually hear are transmitted through the air.

The production of sound

Sound is produced by the vibration of an object, such as a guitar string, a person's vocal cords, or a speaker's cone. Together, these vibrations push neighboring air molecules while slightly increasing the air pressure.

The air molecules under pressure then push the surrounding air molecules, which in turn push the next group of molecules, and so on. When a high-pressure area passes through the air, it leaves a low-pressure area behind. When changes in these pressure waves reach the human ear, they vibrate the nerve endings in the ear, and our auditory centers perceive these vibrations as sounds.

The sound travels through the medium to the ear drum, which also vibrates at the same rate. Everything that makes sound vibrates, the vibration stops, and the sound stops. A vibrating object is called a sound source.