1) Sound waves are a form of mechanical wave that travel through mediums such as air or water by causing vibrations of particles in the medium. 2) Frequency is measured in Hertz and determines the pitch of the sound wave, with higher frequencies corresponding to higher pitches that humans can hear between 20-20,000 Hz. 3) Intensity refers to the amount of energy transported by the sound wave and is measured in Watts/meter^2, decreasing with distance from the source.

1. SOUND WAVES IN
INSTRUMENTS
BY SAMANTHA YANG

2. LET’S START WITH THE BASICS…
• A wave is the motion of a disturbance, sometimes with a medium, sometimes without
• A mechanical wave travels through a medium, or physical material
• Sound waves are a form of mechanical wave that may travel through mediums such as water or air
• Sound waves are a longitudinal wave, which means the direction of the particles of the medium is parallel to
the energy transport
• A sound wave is introduced by a vibrating object such as a violin string or a tuning fork

3. A WAVE TRAVELING THROUGH A MEDIUM

4. PITCH AND
FREQUENCY
• Frequency is measured in Hertz which may be defined as vibration(s)/second
• Pitch is how high or low the sound is perceived
• Humans can hear from a range of 20Hz to 20,000Hz
• The higher the frequency, the higher the pitch
• Lower frequencies tend to be louder

5. AN EXAMPLE
For any guitar players out there, here is a table of the frequency of each string- note the trend of lower
notes decreasing in frequency

6. CHECK FOR UNDERSTANDING
John built a frequency counter that measures frequency. Testing it out, he found that the highest note of his
favorite song is 24,000Hz. Is this reasonable? Explain why or why not.
• No it is not because humans can only hear from 20 to 20,000 Hz of frequencies
What causes a mechanical wave?
• A disturbance or vibration
Is it possible for a wave to travel without a medium? List an example
• Yes, electromagnetic waves may travel in a vacuum or through space

7. INTENSITY
• The amount of energy that is transported past a given area of the medium per unit of time is known as
the intensity of the sound wave
• Units of intensity are Watts/meter2
• Intensity may also be measured in decibels
• As a sound wave carries its energy through a two-dimensional or three-dimensional medium, the
intensity of the sound wave decreases with increasing distance from the source.

8. INTENSITY OF INSTRUMENTS
• Piano – 60 to 70 decibels
• Cello – 82 to 93 decibels
• Violin – 80 to 103 decibels
• Flute – 93 to 111 decibels
• Trombone – 85 to 114 decibels

9. SOME USEFUL FORMULAS…
• Speed = Wavelength/ Period = Wavelength(Frequency) => v = f • λ
• Linear mass density = Total Mass of string / Length of string => μ = M/L
• Intensity = Power/Area => I = P/A

10. CITATIONS
• Linden, Joshua. "Pitch and Frequency." Pitch and Frequency. The Physics Classroom, 3 Dec. 2013. Web.
11 Feb. 2015.
• Marshall, Chase. "H.E.A.R. Are You At Risk?" H.E.A.R. | Are You At Risk? | Hearing Education and
Awareness for Rockers. H.E.A.R Net, 14 Jan. 1998. Web. 18 Feb. 2015.
• Wolfe, Joe. "Strings, Standing Waves and Harmonics." Strings, Standing Waves and Harmonics.
University of New South Wales, 11 Oct. 2011. Web. 13 Feb. 2015.