WHAT IS SOUND? |
When you hear any sound – even a CRASH! or a BANG!, it is made by air that is moving back and forth or vibrating. The same is true for sounds made by musical instruments. The difference between NOISE and MUSIC is that musical sounds are organized into patterns that have pitch and rhythm. Noise is unorganized sound or sounds. Sounds are made and travel in the same way whether they are musical sounds or noise.
Sound is a type of energy made by vibrations. When any object vibrates, it causes movement in the air particles. These air particles are called molecules. 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. Picture a stone thrown into a still body of water. The rings of waves expand indefinitely. The same is true with sound. Irregular repeating sound waves create noise, while regular repeating waves produce musical notes. |
| HOW DOES SOUND TRAVEL? |
Sound travels through air that moves or vibrates. These vibrations are called waves. Sound waves can also travel through the vibration of water, wood or any other material. A musical sound is called a tone. It is produced by air that vibrates a certain number of times per second. These sound waves must be controlled in some way that the performer can manage the loudness, the special feature of the tone, and how long it plays.
Most musical instruments have a reed, a string, or some other device that creates sound waves when moved. Sounds are different because of harmonics, which are higher and quieter sounds mixed in. Harmonics are not heard separately, but add to the tone of the sound. This is what makes the instruments sound differently from one another. |
| WHAT IS FREQUENCY OR PITCH? |
The number of times that a sound wave vibrates in a second is called its frequency. Another word that can be used for frequency is pitch. Pitch indicates whether a note is high or low. Scientists even have a name for how they measure the frequency of sounds. They measure it in cycles and call it hertz.
High notes have a higher frequency than lower notes and this changes their shape. Different types of sound waves have different shapes. Sounds waves can be seen, heard and measured on a special scientific instruments. One such instrument is a sound level meter.
When the vibrations are fast, you hear a high note. When the vibrations are slow, it creates a low note. The sound waves in the diagram show the different frequencies for high and low notes after one second of vibrations. When the oboe tunes the orchestra, the pitch he uses is vibrating at 440 vibrations per second.
|
| WHAT IS A DECIBEL? |
A decibel is the unit used to measure the power of a sound. Just as a ruler can use inches, feet and yards to indicate how long or short something is, a decibel indicates how loud or soft a sound is.
On the decibel scale, the smallest audible sound (near total silence) is 0 dB. A sound 10 times more powerful is 10 dB. A sound 100 times more powerful than near total silence is 20 dB. A sound 1,000 times more powerful than near total silence is 30 dB. Here are some common sounds and their decibel ratings:
- Near total silence – 0 dB
- A whisper – 15 dB
- Normal conversation – 60 dB
- A lawnmower – 90 dB
- A car horn – 110 dB
- A rock concert or a jet engine – 120 dB
- A gunshot or firecracker – 140 dB
Distance can affect the power of sound. If you are far away, the power is greatly reduced. All of the above ratings were taken while standing near the sound. |
| WHAT IS TIMBRE? |
The same note will sound different when played on a piano or on a violin. The special feature or character of a sound that sets it apart from other sounds is called “timbre”. It is pronounced “tam-ber”. It is also called “tone color”. The pitch and loudness of a sound are not usually considered part of its timbre because a violin still sounds like a violin regardless of what notes it plays or how loudly they are played. Some of the words used to describe timbre are:
- Bright
- Warm
- Harsh
- Wavering
- Noisy
- Nasal
- Pure
- Gradual
- Metallic
- Wooden
- Breathy
- Weird
|
SOUND & HEARING
|
Did you wonder how you were able to hear the beautiful music that was played by the orchestra for you today? Well, it’s all related to those sound waves you’ve read about. When sound waves reach your ear, they pass into the ear through a funnel-shaped passage called the ear canal. The ear canal directs the sound onto a tiny drum-like covering between the outer and inner ear. This is the eardrum. The eardrum vibrates along with the vibrations of the incoming air. Even if the sound is very loud, the eardrum only moves slightly.
Then three bones move along with the eardrum. They push into the cochlea. The cochlea is a coiled tube in the inner ear which is filled with fluid. The three bones cause wiggling in a tiny covering inside the cochlea. These movements are changed into electrical impulses which are passed to nerves. These nerves send messages to and from the brain. The pulses send information about pitch and how loud the sound is. Then you identify sounds from these pulses.
WOW! What an amazing process.
Click on the labels above for the definitions.
Back |
|
