What are the physical principles of sound, the properties of physical sound

1. Sound production:

1. Sound is produced by the vibration of an object; (People vibrate their vocal cords to make sounds, bees vibrate their voices by small black dots under their wings, and the wind sounds.)

It is the sound of air vibration, the vibration sound of the air column in the test of controlled instruments, and the stringed instruments.

The sound is produced by the vibration of the strings, and the vibration of the drum is produced by the vibration of the drum surface.

sound, bell test bell vibrating sound, etc.);

2. Vibration stops, and stops; But the sound did not immediately disappear (because the original sound continued to spread);

3. The emitter can be solid, liquid and gas;

2. Sound propagation.

1. The propagation of sound requires a medium; Solids, liquids, and gases can all transmit sound; The sound travels with minimal loss when propagating in solids.

In general, sound travels fastest in solids and the slowest in gases (cork.

except); 2. Vacuum can't transmit sound, the moon.

Astronauts on (in space) can only talk wirelessly**;

3. Sound propagates in the form of waves (sound waves);

3. How to hear voices.

1. The composition of the human ear: The human ear is mainly composed of the external auditory canal.

tympanic membrane, ossicles, cochlea, and auditory nerve;

2. The sound is transmitted to the ear canal, causing the eardrum to vibrate, and then transmitted to the brain through the ossicles and auditory nerve to form hearing;

3. In the process of sound transmission to the brain, any part of the body is blocked, and the person will lose hearing (the eardrum and ossicles are blocked.

conductive hearing loss; Disorders of the auditory nerve are neurological hearing loss.

4. Bone conduction: without the help of the eardrum, by the skull and jaw.

to the auditory nerve, which in turn to the brain to form hearing (Beethoven.

Deafness after hearing. **, our own voice that we hear ourselves when we speak); The performance of bone conduction is better than that of air sound;

5. Binaural effect: the distance from the source to the two ears is generally different, so the time, strength and pace of sound transmission to the two ears are also the same.

is different, and the phenomenon of judging the direction of the sound source (hearing stereo.

There are three characteristics of physical sound: pitch and loudness.

Timbre. <>

1. The concept of tone.

In physics, the pitch of a sound is called pitch.

It should be noted here that the level of the voice in the concept is different from the level of the voice we understand in life, in life, we often refer to the size of the voice, the meaning of speaking loudly and speaking quietly; In physics, the level of sound refers to the thickness and sharpness of the sound.

2. Loudness: The strength of the sound is called loudness.

Amplitude. The maximum distance that an object deviates from its original position when it vibrates is called the amplitude.

Factors that determine the magnitude of loudness: amplitude, distance from the emitter. The greater the amplitude, the greater the loudness.

Experimental: Factors that affect loudness.

Design experiment: Tie a table tennis ball to a string.

Tap the tuning fork that is making a sound.

Observe how much the ping-pong ball is bounced off. Make the tuning fork sound with different loudness, and redo the above experiment.

Phenomenon: When struck with different forces, the ping ball is bounced at different heights. The greater the force, the higher the table tennis ball will be bounced.

Conclusion: The amplitude of the emitter determines the magnitude of loudness, and the larger the amplitude, the greater the loudness.

Note: The function of the table tennis ball: to amplify the small vibrations of the tuning fork.

3. Timbre: reflects the quality of the sound.

We can distinguish different sounds based on different timbres. The timbre is determined by the emitter itself. The materials and structures of different emitters are different, and the timbre of the sound produced is also different.

1.Propagation of soundThe sound of the object should vibrate, and the vibration should stop and the sound should stop.

Sound propagation depends on the medium, and a vacuum cannot transmit sound.

Usually the sound velocity is 340m s, and the sound velocity is faster than the liquid.

2.Characteristics of soundThere are three types of sound characteristics, pitch, loudness, and timbre.

The vibration speed of the fierce object corresponds to the pitch.

The frequency of vibrations (times) per second, in hertz (Hz).

The human ear can hear from 20 to 20,000 Hz

The amplitude of the object, the intensity of the sound, and the loudness.

Different sounds are distinguished, and sound waves have different timbres.

3.Noise hazards and controlSounds that interfere with people resting, studying and working, and disturbing listening are all common noises.

The sound level is decibels (db), and the weak sound is 0

In order to protect hearing, the lead bridge sound should not exceed 90 (db).

Ensure work and study, and the voice does not exceed 70 (db).

Make sure you are resting and sleeping, and your voice does not exceed 50 (db).

There are three stages of noise attenuation, sound source, propagation and human ear branch digging.

There are two types of use of sound, which convey information and energy.

Eat up the physical characteristics of sound – loudness and timbre.

Listen to the physics allegro "The Characteristics of Sound" and explain it.

No matter how loud it is.

How often. In the same substance.

speed of propagation.

is unchanging.

Grade 8 Physics Volume I, Chapter 1: The Production of Sound.