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What causes sound to change pitch while stirring a cup of coffee?
Wiki User
∙ 15y ago
I have been looking into this and i think the following may combine to produce this effect. Either/and/or. 1. As you stir the liquid is forced up at the sides and down in the middle. This increases the area in contact with the liquid. 2. As the hot liquid is poured into the cup/mug, it gradually heats the ceramic which changes the pitch. To test this, pour hot water into a cold cup/mug and tap a spoon on the lip. While the liquid remains still, the pitch gradually goes up as the ceramic heats up. You could also try different materials to see what happens, e.g. plastic or glass. Put your results here if you like. Try hot and cold liquids also and try stirring them to see if there is a change in pitch. Also bear in mind research has apparently been done on this, see the post below: http://www.physicsforums.com/archive/index.php/t-18996.html tiny-tim
Mar8-08, 07:37 PM
Something else: why does the pitch sound different when you tap a spoon to the bottom of a cup with spinning (hot) liquid compared to when the liquid is not spinning?
You can actually hear the pitch change when you first stir it very well, start tapping until the vortex slows down.. it's my dad's favorite scientific experiment ;)
Hi Monique!
A very similar issue was examined in the Proceedings of the Cambridge Philosophical Society, volume 65, page 365 (1967), in an experimental research paper entitled:
On note emitted from a jug while mixing instant coffee.
The authors were Farrell W.E. (whose usual field seems to be plate tectonics), Mackenzie D.P., and Parker R L.
Unfortunately, my library has no volumes before volume 77, but from memory they discovered that the note depends on the density of air molecules trapped against the coffee grains - which changes as you stir it!
Well … it was the sixties … and that sort of thing was important … :smile:
(I know this is almost a duplicate of a post in another thread
- but I thought it was important)
Wiki User
∙ 15y ago
While stirring a cup of coffee, the pitch of the sound changes because the speed of the stirring affects the frequency at which the coffee is being agitated. Faster stirring results in higher frequency vibrations, creating a higher pitched sound, while slower stirring produces lower frequency vibrations and a lower pitched sound.
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The pitch change in our voice is primarily caused by the tension in our vocal cords. When the vocal cords are stretched and tightened, they vibrate faster, producing a higher pitch. Conversely, when the vocal cords are relaxed and less tense, they vibrate slower, resulting in a lower pitch.
A siren is moving past Mary as she sits stuck in traffic To Mary the pitch of the siren changes as it passes her position What causes this to happen?
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Why Doppler effect causes the change in sound?
The Doppler effect causes a change in sound because of the relative motion between the source of the sound and the observer. When the source is moving towards the observer, the sound waves are compressed, leading to a higher frequency (higher pitch). When the source is moving away, the sound waves are stretched, resulting in a lower frequency (lower pitch).
How does the pitch of a harmonica change?
The pitch of a harmonica changes when you blow or draw air through different reeds. The reeds are tuned to different pitches so when you blow or draw, the airflow causes them to vibrate at different frequencies, producing different notes.
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What causes pitch to change?
Every sound vibrates with a particular fundamental frequency. When you change the wavelength of a sound, you change the pitch of a sound.
What effect causes a siren to change in pitch as it passes by?
doppler effect
What is the name of the effect the causes the pitch of an ambulance siren to change as it passes you?
The Doppler effect
What causes the pitch change of our voice from high to low?
The pitch change in our voice is primarily caused by the tension in our vocal cords. When the vocal cords are stretched and tightened, they vibrate faster, producing a higher pitch. Conversely, when the vocal cords are relaxed and less tense, they vibrate slower, resulting in a lower pitch.
What causes a car horn to change pitch as the car passes you?
The car's horn doesn't change pitch. As you pass by the Doppler Effect happens. The sound waves get increasingly loud then fade away and become increasingly quiet.
How does loosening a string change the sound of a guitar string?
It causes the string to vibrate more slowly, decreasing the pitch (frequency).
A siren is moving past Mary as she sits stuck in traffic To Mary the pitch of the siren changes as it passes her position What causes this to happen?
The Doppler effect causes the pitch of the siren to change as it moves past Mary. As the siren approaches, the sound waves are compressed, resulting in a higher pitch. As it moves away, the sound waves are stretched, resulting in a lower pitch. This change in frequency creates the perception of the siren's pitch changing.
How does the pitch of a harmonica change?
The pitch of a harmonica changes when you blow or draw air through different reeds. The reeds are tuned to different pitches so when you blow or draw, the airflow causes them to vibrate at different frequencies, producing different notes.
Who discovered the red shift in stars the same effect that causes sound waves to change pitch as an object moves towards or away from an observer?
Doppler.
What must change in order for the pitch of a sound change?
The frequency of the sound wave must change in order to change the pitch of a sound. A higher frequency results in a higher pitch, while a lower frequency results in a lower pitch.
How xylophones change pitch?
You can use a different stick to hit it and it should change pitch
How do you change the pitch of a tambourine?
By tightening the head, skin or vellum. The tighter the head the higher the pitch. Advanced percussionists can change the pitch while playing by pressing down gently on the middle of the head while hitting the instrument. This causes a fluctuation the pitch of each stroke.
