Name __________________________________________
Sound Notes: Part II
The Speed of Sound
The speed of sound depends only on the ___________________________________________________________.
Does the speed of a sound wave depend on the frequency? ______ The wavelength? _____ The amplitude? _____
In general, sound travels fastest through _________________________. This is because molecules in a solid medium are
__________________________________________ than those in a liquid or gas, allowing sound waves to travel more
quickly through it. In fact, sound waves travel over _____ times faster through steel than through air.
Sound also travels faster in ________________________ than in gases because molecules are still more tightly packed.
In fresh water, sound waves travel _____ times faster than in air!
The speed of sound through a gas depends on the___________________________. When we look at the properties of
a gas, we see that only when molecules _________________________ with each other can the compressions and
rarefactions of a sound wave be passed along. So, it makes sense that the speed of sound depends on how ___________
the particles collide. At higher temperatures, molecules _______________________ more often, giving the sound wave
more chances to move forward rapidly.
The Pitch of Sound
What characteristic of a sound wave determines the pitch of the sound? ___________________________________
What is the relationship between the frequencies of two music notes one octave apart? _______________________
The frequency or frequencies at which an object tends to vibrate with when hit, struck, plucked, strummed or somehow
disturbed is known as the_____________________________ of the object.
Some objects tend to vibrate at a single frequency and they are often said to produce a ____________________. A flute
tends to vibrate at a single frequency, producing a very pure tone. Tuning forks also produce a pure tone.
Other objects vibrate and produce more complex waves with a set of frequencies that have a whole number
mathematical relationship between them; these are said to produce a _________________________. A tuba tends to
vibrate at a set of frequencies that are mathematically related by whole number ratios; it produces a rich tone.
Still other objects will vibrate at a set of multiple frequencies that have no simple mathematical relationship between
them. These objects are not musical at all and the sounds that they create could be described as _________________.
Example:
Name __________________________________________
The same note from different instruments has different qualities because the sounds from instruments are rarely pure
notes, i.e. of one frequency.
Rather they consist of one main note which is predominant and other smaller notes called ______________________.
The main note or fundamental note is also referred to as the ___________________ harmonic and if it has a frequency
f, the overtone with frequency 2f is called the __________________ harmonic and the overtone with frequency 3f is
called the __________________________ harmonic and so on. The sum of all the harmonics is the waveform and
determines the quality of the sound.
The Doppler Effect
The Doppler Effect is a phenomenon observed whenever the source of waves is __________________ with respect to an
observer.
The Doppler Effect is an apparent _____________ shift in frequency for the observer when the source is approaching,
and an apparent ______________________ shift in frequency when the source is receding.
The source of sound always emits the ________________________ frequency. Therefore, for the same period of time,
the same number of waves must fit between the source and the observer. If the distance is large, then the waves can be
__________________________________; but if the distance is small, the waves must be compressed into the ________
distance. For these reasons, if the source is moving towards the observer, the observer perceives sound waves reaching
him or her at a more frequent rate (______________________________). And if the source is moving away from the
observer, the observer perceives sound waves reaching him or her at a less frequent rate (___________________). It is
important to note that the effect does not result because of an actual change in the frequency of the source.
For the Doppler Effect to occur, the source may be moving, the listener may be moving, or ___________ may be moving.
Name __________________________________________