How does vibration produce sound waves

For example, we would not be able to hear the slow vibrations that are made by waving our hands in the air. The slowest vibration human ears can hear is 20 vibrations per second. That would be a very low-pitched sound. The fastest vibration we can hear is 20, vibrations per second, which would be a very high-pitched sound. Cats can hear even higher pitches than dogs, and porpoises can hear the fastest vibrations of all up to , times per second! Pitch is related to frequency, but they are not exactly the same.

Frequency is the scientific measure of pitch. That is, while frequency is objective, pitch is completely subjective. Sound waves themselves do not have pitch; their vibrations can be measured to obtain a frequency, but it takes a human brain to map them to that internal quality of pitch.

The pitch of a sound is largely determined by the mass weight of the vibrating object. Generally, the greater the mass, the more slowly it vibrates and the lower the pitch. However, the pitch can be altered by changing the tension or rigidity of the object. For example, a heavy E string on an instrument can be made to sound higher than a thin E string by tightening the tuning pegs, so that there is more tension on the string.

Nearly all objects, when hit, struck, plucked, strummed or somehow disturbed, will vibrate. When these objects vibrate, they tend to vibrate at a particular frequency or set of frequencies. This is known as the natural frequency of the object.

It will make this same sound every time. This sound can be changed, however, by altering the vibrating mass of the glass.

Sound wave consists of vibrating particles. These knock into other particles causing them to vibrate, and so the sound can travel away from the source. You can hear sound because the vibrations in the air cause your ear drums to vibrate. This vibration is converted into signals which travel down a nerve to your brain. And similarly, microphones can detect these vibrations and convert them into electrical signals.

When you think about a sound wave, you may think of something that looks a little bit like a water wave like this, but this a really inaccurate representation of the sound wave.

The particles moving a part of a sound wave vibrate back and forth in the direction that the sound wave is travelling, creating areas where the particles are more bunched up, high pressure, and areas where the particles are more spread out, low pressure. Now, this type of wave is called a longitudinal wave. In this case, the x-axis of the graph is space. So the graph represents a sound wave passing a particular point.

From a graph showing how the wave changes over time, we can extract two important features. The amplitude of the wave is the height of the wave on the graph from the middle to its highest point. Now, louder signs will produce waves with a higher amplitude.

The sound wave created by an actor projecting their lines across a theatre will have a higher amplitude than somebody in the audience whispering to their friend. The time between two peaks on one of these graphs is the time period of the sound. And to get the frequency of the sound, you must calculate one divided by this time period. The frequency of sound tells us about the pitch of the sound that you hear.

A sound wave with a higher frequency will have a higher pitch. The shrill sound of a whistle will look a lot more bunched up on one of these graphs than the deep sound of a double bass. Of course, most sound waves are not pure sounds like this one. Most sounds are made up of combination of lots of these waves. As you can see, whistling gives a nice, pure sound, whereas the sound wave from speech is a combination of multiple waves of different frequencies and amplitudes into a more complicated wave.

When the vibrations are fast high frequency , you hear a high note. When vibrations are slower, you hear a lower note. Describe how sound is produced. How many different vibrations are needed to hear a sound? All objects have the potential to vibrate. Can we hear all of them? If a tree falls in a forest and there is nobody around to hear it, does it still make a sound? Teacher Tip: This demonstration is a good way to introduce the topic of sound. Details Activity Length 10 mins. In this demonstration, students use their bodies to model vibrations that lead to sound waves.

Three things vibrate when sound is created: the source object the molecules in the air or another medium e. Objectives Describe how sound is produced. This enables sound waves to rapidly transfer vibrations from one molecule to another. Sound moves similarly through water, but its velocity is over four times faster than it is in air.

The speed of sound is dependent on the type of medium the sound waves travel through. When supersonic aircraft fly overhead, a local shockwave can be observed! Generally, sound waves travel faster in warmer conditions. As the ocean warms from global climate, how do you think this will affect the speed of sound waves in the ocean?

When an object vibrates, it creates kinetic energy that is transmitted by molecules in the medium. As the vibrating sound wave comes in contact with air particles passes its kinetic energy to nearby molecules. As these energized molecules begin to move, they energize other molecules that repeat the process.

Imagine a slinky moving down a staircase. As the first ring expands forward, it pulls the rings behind it forward, causing a compression wave. Sound waves are composed of compression and rarefaction patterns. Compression happens when molecules are densely packed together. Alternatively, rarefaction happens when molecules are distanced from one another.

As sound travels through a medium, its energy causes the molecules to move, creating an alternating compression and rarefaction pattern. It is important to realize that molecules do not move with the sound wave.

As the wave passes, the molecules become energized and move from their original positions. During compression there is high pressure, and during rarefaction there is low pressure. Different sounds produce different patterns of high- and low-pressure changes, which allows them to be identified. The wavelength of a sound wave is made up of one compression and one rarefaction. Sound waves lose energy as they travel through a medium, which explains why you cannot hear people talking far away, but you can hear them whispering nearby.

As sound waves move through space, they are reflected by mediums, such as walls, pillars, and rocks. This sound reflection is better known as an echo. This is due to the large rock walls reflecting your sound off one another. So what type of wave is sound? Sound waves fall into three categories: longitudinal waves, mechanical waves, and pressure waves. Keep reading to find out what qualifies them as such. If you push a slinky back and forth, the coils move in a parallel fashion back and forth.

Similarly, when a tuning fork is struck, the direction of the sound wave is parallel to the motion of the air particles. A mechanical wave is a wave that depends on the oscillation of matter, meaning that it transfers energy through a medium to propagate.

These waves require an initial energy input that then travels through the medium until the initial energy is effectively transferred. Examples of mechanical waves in nature include water waves, sound waves, seismic waves and internal water waves, which occur due to density differences in a body of water. There are three types of mechanical waves: transverse waves, longitudinal waves, and surface waves.

Why is sound a mechanical wave? Sound waves move through air by displacing air particles in a chain reaction. As one particle is displaced from its equilibrium position, it pushes or pulls on neighboring molecules, causing them to be displaced from their equilibrium.

As particles continue to displace one another with mechanical vibrations, the disturbance is transported throughout the medium. These particle-to-particle, mechanical vibrations of sound conductance qualify sound waves as mechanical waves. Sound energy, or energy associated with the vibrations created by a vibrating source, requires a medium to travel, which makes sound energy a mechanical wave.

A pressure wave, or compression wave, has a regular pattern of high- and low-pressure regions. Because sound waves consist of compressions and rarefactions, their regions fluctuate between low and high-pressure patterns. For this reason, sound waves are considered to be pressure waves. For example, as the human ear receives sound waves from the surrounding environment, it detects rarefactions as low-pressure periods and compressions as high-pressure periods.

Transverse waves move with oscillations that are perpendicular to the direction of the wave. Sound waves are not transverse waves because their oscillations are parallel to the direction of the energy transport; however sound waves can become transverse waves under very specific circumstances.