Acoustics in physics, about physical acoustic phenomena?

1.Choose C, after many reflections of the mountain clouds on the ground, the actual propagation distance is large and small, so that we can hear thunder many times, in fact, a lightning itself only produces one thunder. For example, if two mirrors are placed opposite each other or at an angle, we can see many images in the mirror.

b Obviously not right, suppose that there is only one ear, and the thunder can still be heard many times. The usefulness of having two ears in a human or animal is that it can locate the source of sound transmission. d, irrelevant to the problem, simple.

2.Correct, a friend upstairs said that the Doppler effect has nothing to do with this problem, but only occurs when the listener is in relative motion to the sound source. Sound is the vibration in propagation (here the vibration of the air molecules), and when the air is at rest as a whole, the speed of sound is 340m s.

When there is a tailwind, the air itself moves relative to the listener, and of course the sound can be heard earlier, i.e. the actual speed of propagation increases. The vibrations of this part of the air will be blown farther away with the wind, and people in those places will hear the sound (assuming they would not have heard it originally), although the sound they hear is very different from the original sound and is very vague (if far away). If the reverse wind is against the wind, the situation will be reversed.

Now consider an extreme case, assuming that the speed of the wind relative to the listener is also 340m s away from the listener, then the sound will not reach the listener's ears at all (the vibration is just about to be transmitted by the wind and blown away, to be precise, the air carrying the sound vibration signal has been blown away), but such a large wind speed does not seem to be available on the earth, but it can be artificially made, if you want to verify it, do such an experiment.

3.The eardrum, or eardrum, simply vibrates the air that comes through it and becomes its own vibration, not necessarily amplified. Amplification is a complex bioelectrical process that is not directly related to the tympanic membrane.

Upstairs explained from a professional point of view, it should be correct, but the layman may not understand it.

4.When Zhang San pinched the watch, the athlete was already running, and Zhang San's time was actually less than 100m of time, so the time was small. Li Si can basically accurately reflect the actual time, because it basically does not consume time when he sees smoke (the speed of light is too large), Zhang San can't do it, and it takes time to hear the sound of the order, for example, 100m is consumed, and this error cannot be ignored.

1: C2: False, because the speed of propagation of sound is constant, always 340m s, independent of wind direction.

3: The role of the eardrum is to transmit sound, not to amplify it.

4: Zhang San's timer is smaller than Li Si's.

Because the speed of light is faster than the speed of sound, and Zhang San listens to the sound, the post-timing is obviously less, so Zhang San's timer is smaller.

Hope it helps, thank you!! ）

3.The phrase "the eardrum acts as an amplification of the sound waves formed by the vibration of the air" is wrong, and the correct statement is that "the pressure change produced by the vibrating air particles causes the eardrum to vibrate, so that the sound energy is converted into mechanical energy through the structure of the middle ear." Because the tympanic membrane vibrates anteriorly and backward to move the ossicular chain in a piston shape, the surface area of the tympanic membrane is several times larger than that of the stapes foot plate, where sound energy is amplified and transmitted to the middle ear.

Due to the difference in surface area, the sound waves received by the eardrum are concentrated in a smaller space, and the ossicles increase the intensity of the sound by 30 decibels during the energy conversion of sound waves from the eardrum to the vestibular window", which simply means "converting sound energy into vibrations of the ossicular chain" rather than amplifying sound waves.

4.ZHANG San, LI 4.

Since the speed of light is much greater than the speed of sound, seeing smoke depends on light, and hearing gunfire depends on sound, so it is natural to see smoke first and then hear sound; Li Si clocked first, and the number displayed by Li Si was larger.

1. C2, sound wave refraction phenomenon. The wind speed is generally small near the ground and gradually increases on the far ground, which leads to the longitudinal distribution of the sound velocity. When the sound wave propagates against the wind, it will bend upwards to form a shadow area, so the receiver at the same height on the ground will not hear it, which means that the horizontal propagation distance will be closer to the headwind.

3. The specific structure of the ear is not clear, but the eardrum is not necessarily amplified sound waves, it is equivalent to a sensor, which has different responses to different sound waves, some sounds will amplify and some even have almost no response (ultrasound, infrasound).

4. The speed of sound and the speed of light. If the two of them are some distance away from the starting gun, the time will be less likely to start.

1, C2, sound is a type of energy, which travels in the air. Under certain conditions, its propagation speed is constant, with or without wind. Because of the "Doppler effect", the frequency of the sound in the downwind and the sound in the absence or upwind will change.

That's when you're at the station, and when the train gets close to us, the tone of the air horn gets higher. And the reason why the tone gets lower when the train is far away from us.

2.Incorrect type of wave propagation and medium. Temperature related to 3The mistake is to amplify the sound waves (to make them hear more clearly) in order to receive the signal more clearly 4Zhang San has less time than Li Si and the sound propagation time is longer than the light propagation time.

The magnitude of the sound (loudness step, loud and small sound) is determined by the amplitude, and the pitch (high and low tones) is determined by the frequency.

If the two objects in this question are identical, then when the amplitude is the same, but one vibrates at a small frequency and the other vibrates at a high frequency (within the audible range of the human ear), two will be heard with the same loud voice, but one with a high note and the other with a low sound; If two objects vibrate at the same frequency, one with a large amplitude and the other with a small amplitude, then two voices of the same tone but one loud and the other small will be heard.

This is when the elephant escapes.

The speed of the sound is 340m s=1224kmh, and the distance between the waves and the elephant when the elephant hears the sound is 5km-5 1224

So the time from hearing the infrasonic wave to the time of the sea swim is (5km-5*40 1224) 40=minutes.

Solution: Let this section of the road be S meters long. From the meaning of the title: s v1 - s v2 = t

Then: s 340-s 5000 = 2

So: s = A: This section of the road is meters long.

This question is a typical acoustic problem. Generally speaking, the longer the size of the object, the lower the frequency of vibration sound, and in everyday life we use the word "tone" to represent the frequency of sound. For example, generally the taller the person, the lower the voice, because the taller the voice, the corresponding vocal cords are also long, and the vocalization is low vibration frequency, that is, low pitch.

1. The longer the length of the ruler protruding from the tabletop, the slower the vibration (slower), and the lower the tone of the sound;

2. The shorter the length of the ruler protruding from the tabletop, the faster the vibration (faster), and the higher the tone of the sound.

From this, it can be concluded that the pitch is high and low and (vibrational frequency).

1.Slow, high.

2.Fast, low.

Fast and slow are inversely proportional.

It must be the difference in timbre, I think the more expensive materials and workmanship must be better than the cheaper ones, for example: the strength of the magnet, the quality of the wire, the thickness of the paper cone and whether the paper cone is tight will affect its timbre, what you call "a sense of distance" I guess it may be related to the tightness of the paper cone, as for the experiment, I will tell you a method of using the drum to verify that you can maintain the same distance, adjust the tightness of the drum skin, and beat the drum skin with the same strength (this is just an ideal idea, Because it is impossible for a person to do the same dynamics), and then listen to their voices to compare and draw conclusions. In fact, this method is not reliable, because there are too many factors affecting the headphones, if you want to be clear, you must make a simulated headset, keep one variable unchanged, and eliminate such variables (sometimes it will be caused by two or three variables), so it is very difficult.

You can try it the same way I did, hopefully as I guessed.

It's a matter of timbre. As for experiments. You go and ask the teacher.

This should be asked about electronics, and it should be a question of good or bad.

The timbre frequency is different, and the better one has the super bass function (low frequency band).

1) Let the distance from the person to both sides of the valley be x and y, respectively, x2x=340*1

x=170m

A second echo was heard after another 2 seconds.

2y=340*(1+2)

y=510m

The valley is wide. s=x+y=680m

2) Speed of sound v'=340m s, set the speed to V

From the sound of the horn to the hearing of the echo, the distance of the sound is s=700+(700-400)=1000m

The time of the sound transmission s s v'= the time taken by the car to advance 400m 400 V, i.e. 1000 340 = 400 V

Vehicle speed v=136m s

The speed is too high and unrealistic. Did you hear an echo after 40 meters of progress? If you hear an echo after 40 meters of progress, then (700+700-40) 340=40 V, V=10M S=36km H, which is more realistic.

The valley is 680 meters wide and the speed is about 35 m s