How is sound produced

Other sounds, such as a dog whistle, are inaudible to the human ear. This is because dog whistles produce sound waves that are below the human hearing range of 20 Hz to 20, Hz. Waves below 20 Hz are called infrasonic waves infrasound , while higher frequencies above 20, Hz are known as ultrasonic waves ultrasound. Infrasonic waves have frequencies below 20 Hz, which makes them inaudible to the human ear.

Scientists use infrasound to detect earthquakes and volcanic eruptions, to map rock and petroleum formations underground, and to study activity in the human heart. Despite our inability to hear infrasound, many animals use infrasonic waves to communicate in nature. Whales, hippos, rhinos, giraffes, elephants, and alligators all use infrasound to communicate across impressive distances — sometimes hundreds of miles! Sound waves that have frequencies higher than 20, Hz produce ultrasound.

Because ultrasound occurs at frequencies outside the human hearing range, it is inaudible to the human ear. Some lesser-known applications of ultrasound include navigation, imaging, sample mixing, communication, and testing.

In nature, bats emit ultrasonic waves to locate prey and avoid obstacles. Sound is produced when an object vibrates, creating a pressure wave. This pressure wave causes particles in the surrounding medium air, water, or solid to have vibrational motion. As the particles vibrate, they move nearby particles, transmitting the sound further through the medium.

The human ear detects sound waves when vibrating air particles vibrate small parts within the ear. In many ways, sound waves are similar to light waves. They both originate from a definite source and can be distributed or scattered using various means.

Unlike light, sound waves can only travel through a medium, such as air, glass, or metal. We know that sound can travel through gases, liquids, and solids. But how do these affect its movement? Sound moves most quickly through solids, because its molecules are densely packed together. 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.

This is because you have muffled one of your ears, and therefore weakened your ability to use signals about the timing or intensity of the sounds reaching each ear. When audio engineers create three-dimensional audio 3D audio , they must take into consideration all the cues that help us locate sound, and they must use these cues to trick us into perceiving sound as coming from a particular location.

Even though with 3D audio there are a limited number of physical sound sources transmitting via headphones and speakers for example, only two with headphones , the audio can seem like it is coming from many more locations.

For example, if an audio engineer wants to create a sound that seems like it is coming from in front of you and slightly to the right, the engineer will carefully design the sound to first start playing in the right headphone and to be slightly louder in this headphone compared with the left. Video games and movies become more immersive and life-like when paired with these tricks of 3D audio.

When watching a movie, for example, sets of speakers within the movie theater can focus the sound direction to allow for a match between what you are seeing and what you are hearing. For example, imagine that you are watching a movie and an actress is having a phone conversation on the right side of the screen.

Her speech begins to play mostly through the right speakers, but as she moves on the screen from right to left, the sound follows her gradually and smoothly. This effect is the result of numerous speakers working in tight synchrony, to make the 3D audio effect possible. Virtual reality VR takes this immersive experience to a higher level by changing the direction of the sound based on where you are looking or are positioned in virtual space.

In VR, by definition, you are virtually placed in a scene, and both the visual and auditory experiences should mirror your experience of the real world. In a successful VR simulation, the direction of your head movements and where you are looking determine where you perceive the audio as originating from. Look directly at a space ship and the sound of its engines come from straight ahead of you, but turn to the left and now the sound comes at you from the right. Move behind a big object and now the virtual sound waves hit the object directly and hit you indirectly, dampening the sound and making it more seem muffled and quieter.

Research scientists and professionals in the film and video game industry have used simulated sounds to learn more about hearing, and to enhance our entertainment experiences. Some scientists focus on how the brain processes sounds, while others analyze the physical properties of sound waves themselves, such as how they bounce or are otherwise disrupted. Some even investigate how other animals hear and compare their abilities to our own.

In turn, professionals in the film and video game industries have used this research to help make the experience of movie-goers and gamers more immersive. In virtual environments, designers can make virtual sound waves behave like sound waves do in real life.

When you are playing a video game or watching a movie, it is easy to take for granted the research and time that went into creating this experience.

Maybe the next advancement in immersive sound technology will start with you and your own curiosity about sound waves and how the auditory system works! The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Music, voices, public address messages… what they all have in common is sound.

If you want to know what it is and which mechanism generates and transmits it, keep reading. The sound is a physical phenomenon that occurs when the vibrations of a transmitter body pass through a fluid or an elastic medium, and then they are perceived by the ear or any other receiver. An elastic medium can be air, water or solid materials such as iron, plastic or copper. The science of acoustics study both sound itself and all the phenomena associated with it its propagation, its properties and its generation.

Acoustics can adopt two different perspectives:. Energy is traveling across the room here, but air itself is not traveling across the room. Only the disturbance within the air is traveling across the room. If air were being transported across the room, it'd be better characterized not as sound but as wind. So, this is why we call sound a sound wave, because it shares the defining feature of waves, which is being able to transport energy through a medium without having to transport the medium itself.

Medium is a fancy word for the material or substance through which a wave is traveling. Air is typically the medium for situations involving sound waves, but sound waves can travel through all kinds of different materials, like water, metal, or even human flesh and bone, and the fact that sound can travel through human flesh and bone explains something you might have always wondered about, which is, why do our voices sound changes voice so different on audio and video recordings?

The reason for this is that when we're speaking to someone we actually hear two contributions from our voice. We hear the sound wave traveling out of our mouth, through the air, and into our ear, but we also hear the vibration of the sound wave traveling through our flesh and bone, through our skull, and into our eardrum.

But on an audio or video recording, the only part that's recorded is the sound that travels through the air.