Abstract

How is sound created?

How does sound travel?

How do we hear sound?

What is:

Frequency and Wavelength

Amplitude and Volume

Music and Noise

Sound

Sound is one of those things we take for granted, but it plays a significant role in our lives. From the time we are babies we hear and respond to sound. It is even theorized that we hear and respond to sound before we are born.

Because sound is such a part of our lives, I thought you might be interested in learning more about it.

I have been involved in audio and sound work for theater since college. So in the process I have learned a lot about acoustics, sound recording and reproduction. I hope you gain a little insight into the world of sound.

How is sound created?

Sound is created by anything that can vibrate with a frequency detectable by human hearing in a medium our ears can perceive. I am specifically limiting sound to the human hearing range. Elephants can hear sounds lower than humans, and dogs and bats can hear sounds higher than humans.

What is Sound?

Sound is a type of energy made by vibrations. When any object vibrates, it causes movement in the air particles. These particles bump into the particles close to them, which makes them vibrate too causing them to bump into more air particles. This movement, called sound waves, keeps going until they run out of energy. If your ear is within range of the vibrations, you hear the sound. What is Sound

How is sound produced

Not all sounds are produced by objects that vibrate like a string. There are many instruments that create vibrations using air. These instruments are called aerophones, a common one is the whistle.

How does a whistle produce sound

A simple experiment illustrates the basics – purse your lips and blow, or blow across a bottle opening. Whistles are aerophones, a family of instruments that produce sound by forcing an air mass through a restricted space, thus creating vibration. Aerophones include brass, woodwinds, pipe organs and even harmonicas. The typical whistle is constructed of metal, plastic or wood, with metal creating the strongest amplifying effect and wood creating the softest, as it absorbs more sound. How Does a Whistle Work?

Some things that produce sound are not as obvious. For example thunder is created by bodies of are slamming into each other.

How do we hear

Before we start to break down sound into it’s components, lets explore how we hear sound.

What are the components of sound

Now that we know how sound is created lets look at the different elements that make up sound waves.

OK that was a lot to take in so we are going to take these properties of sound and discuss them one at a time.

Waves

Lets start by talking about waves. Waves in sound can be see in the movement of a drum head or the oscillations of a guitar string. Many of the sounds we hear are caused by vibrations.

This shows how complex sound is in the real world. We often see a waveform as a single wave such Sinusoidal Waves as Sound

Now lets play with pitch to understand what the relationship of a note and a pitch Online Tone Generator.

As a reference for how notes on the piano relate to frequency lets look at a chart of piano notes to frequency Piano key frequencies.

Lets look at sound waves created by a human voice. We are going to have someone speak into a microphone. The output of the microphone will be displayed on an oscilloscope which maps voltage against time. This will allow us to see the wave forms of the human voice as lines on a screen.

Types of waves

Waves are classified as transverse & longitudinal waves or the difference between waves in water and waves in air.

Sound Properties

Lets pick up the pace by looking at a number of sound properties at once.

How does sound travel

Lets have a little fun. How about we try a thought experiment.

Sound Loudness

The measurement of sound is done in Decibels. But what is a decibel? Lets find out.

Music vs Noise

This is not a simple topic. Some composers use noise to create music. But most of us have a simpler definition of music vs noise. Here are three definitions of music vs noise

• Music has pleasing effect on ears and mind, whereas noise appears to be irritating and a nuisance

• Music has high frequency and there are recognizable patterns of changes in wavelength and amplitude. On the other hand, noise has low frequency, has irregular wavelengths and produces sudden changes in amplitude and wavelength.

• Music has a combination of frequencies and their harmonics, while noise has no such properties.

• Music is harmony, whereas noise is chaos

• Noise is wild and untamed, whereas music is soothing and appealing to listen to.

• Music is a special category of noise. To some, it is organized noise. On the other hand, noise is nothing but random sounds with no order or rhythm. Difference Between Music and Noise

Parameters of Comparison	Noise	Music
Nature	Noise is random.	Music is ordered.
Definition	Noise is those types of sounds that appear unpleasant to hear.	Music appears pleasant to hear.
Structure	Noise is a type of sound that has a continuous structure.	Music is a kind of sound that has a discrete structure.
Composition	The composition of sounds in the noise ranges from very low frequency to very high frequency in the range within which people can hear.	The composition of sounds in the music has fundamental overtones and frequency.
Categorisation	Noise is categorised as a distribution of spectral power or power spectrum and it resembles the distribution of kinetic molecular theory statistically.	Mathematically, music is categorised as the infinite addition of cosines and sines multiplied by some coefficients.
Reaction	Listening to noise for a long time can irritate and frustrate people and they would not prefer to hear such sounds.	Even after listening to music for hours, people enjoy it.
Constitution	Noise is constituted of low frequency, irregular wavelength and waveform.	Music is constituted of harmonious wavelength, waveform and frequency.
Example	Examples of noise is the sound produced by vehicles and crackers.	Examples of music are the sounds produced by flute, piano, guitar.

Difference Between Noise and Music (With Table)

The distinction between music and noise is mathematical form. Music is ordered sound. Noise is disordered sound.

Music and noise are both mixtures of sound waves of different frequencies. The component frequencies of music are discrete (separable) and rational (their ratios form simple fractions) with a discernible dominant frequency. The component frequencies of noise are continuous (every frequency will be present over some range) and random (described by a probability distribution) with no discernible dominant frequency. The Physics Hupertextbook - Music and Noise

Interesting Properties

Now that we have explored some of the properties of sound, lets look at some different properties.

Beats

When you have two sounds that are close to each other in pitch they interact with each other.

Harmonics

When a note is played on a instrument the sound does not sound like a pure sine wave. This is because the notes contains both the primary note plus the harmonics.

Home Work

Yes I am going to recommend a few sources you should explore on your own. There are three sections. Choose any or all of them to explore sounds on your own.

Sound as a Physics Experiment

Demonstrations in Physics was an educational science series produced in Australia by ABC Television in 1969. The series was hosted by American scientist Julius Sumner Miller, who demonstrated experiments involving various disciplines in the world of physics.

Test Your Ears

Guess the sound.

Science Vs. Music

An interesting demonstration of sound and vibrations. The first video is lets you hear and see sound waves. The rest of the videos are interesting auditory experiences beautifully produced.