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Overview of pitch:[3]

Pitch is determined by how many times a sound wave repeat itself within one second of time.

• Each repetition of a waveform is called a cycle.
• The number of repetitions that occur per second is called the frequency.
• Frequency is measured as cps = cycles per second or in Hz called hertz.

“Hz” is derived from the name of Heinrich Hertz, a German scientist who did pioneering work in electromagnetic waves during the 19th Century.

Fig3

The Closer the peaks are together, the higher the pitch.

Fig4

When a frequency is doubled, we get an octave!

Fig5

Pitch helps us distinguish between low and high sounds. When a singer sings the same note twice, one an octave above the other a difference between these two sounds is heard. That is because their pitch is different.

Pitch depends on the frequency of a sound wave. Frequency is the number of wavelengths that fit into one unit of time. A wavelength is equal to one compression and one rarefaction. Even though the singer sings the same note, because the sounds have different frequencies, we hear them as different.

Frequencies are measured in hertz. One hertz is equal to one cycle of compression and rarefaction per second. High sounds have high frequencies and low sounds have low frequencies. Thunder has a frequency of only 50 hertz, while a whistle can have a frequency of 1,000 hertz.

The human ear is able to hear frequencies of 20 to 20,000 hertz. Sounds having frequencies below 20 hertz are known as infrasonic and sounds having frequencies above 20,000 hertz are known as ultrasonic sounds. Some animals can hear sounds at even higher frequencies. The reason we cannot hear dog whistles, while they can, is because the frequency of the whistle is too high be processed by our ears. In other words sounds that are too high for us to hear are called ultrasonic and sounds that are too low for the human ear to hear are called Infrasonic.

Fig6

Schematic diagram showing Ultrasonic and Infrasonic

Frequencies are grouped as:

·         low (bass) - sounds of thunder and gunshots

·         midrange - a telephone ringing

·         high (treble) - small bells and cymbals

o    Low frequencies make the sound powerful and warm

• Midrange frequencies give sound its energy.

Humans are most sensitive to midrange frequencies.

• High frequencies give a sound its "presence" and life like quality.

Presence of a sound enables us to hear it clearly and gives us the feeling that we are close to its origin.