Dumb Question About Trees Falling in a Fores

Oops. Yes, of course. I was thinking about me (this is normal).

The forest in question is a strange forest. All of the animals (and insects, and other lifeforms

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) have been banished by an evil sorceress, indefinitely, for unspecified reasons. Or let's assume so. Does the tree still make a sound?

I know. It's pointless, isn't it - as has been pointed out about 3 times already. It all depends on how you define sound.

I can. Did you mean that I shouldn't?

 

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Wiki definition of sound:

http://en.wikipedia.org/wiki/Sound


Sound
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This article is about compression waves. For other uses, see Sound (disambiguation).
Sound is a disturbance of mechanical energy that propagates through matter as a wave. Sound is characterized by the properties of sound waves which are frequency, wavelength, period, amplitude and velocity or speed.

Contents [hide]
1 Explanation
2 Perception of sound
3 Speed of sound
4 Sound pressure
5 Sound pressure level
5.1 Examples of sound pressure and sound pressure levels
6 References
7 Measurement of sound
8 See also
9 External links



[edit]
Explanation
Noise and sound often mean the same thing, when they differ a noise is an unwanted sound. In science and engineering noise is an undesirable component that obscures a signal.

Humans perceive sound by the sense of hearing. By sound, we commonly mean the vibrations that travel through air and can be heard by humans. However, scientists and engineers use a wider definition of sound that includes low and high frequency vibrations in air that cannot be heard by humans, and vibrations that travel through all forms of matter, gases, liquids and solids. The matter that supports the sound is called the medium. Sound propagates as waves of alternating pressure, causing local regions of compression and rarefaction. Particles in the medium are displaced by the wave and oscillate. The scientific study of sound is called acoustics.

[edit]
Perception of sound

A schematic representation of hearing. (Blue: sound waves. Red: eardrum. Yellow: cochlea. Green: auditory receptor cells. Purple: frequency spectrum of hearing response. Orange: nerve impulse.)Sound is perceived through the sense of hearing. Humans and many animals use their ears to hear sound, but loud sounds and low frequency sounds can be perceived by other parts of the body through the sense of touch. Sounds are used in several ways, most notably for communication through speech or, for example, music. Sound can also be used to acquire information about properties of the surrounding environment such as spatial characteristics and presence of other animals or objects. For example, bats use echolocation, ships and submarines use sonar, and humans can determine spatial information by the way in which they perceive sounds.

The official human hearing range is 20 Hz to 20,000 Hz; however, the majority of people can no longer hear 20,000 Hz by the time they are teenagers and the upper edge only continues to decrease as age increases. The hearing range varies by individual and, mostly in the upper part of the range, hearing damage accumulates with age. The ear is most sensitive to frequencies around 1000-3,500 Hz. Sound above the hearing range is known as ultrasound, and that below the hearing range as infrasound.

The amplitude of a sound wave is specified in terms of its pressure. The human ear can detect sounds with a very wide range of amplitudes and so a logarithmic decibel amplitude scale is used. The quietest sounds that humans can hear have an amplitude of approximately 20 µPa (micropascals) or a sound pressure level (SPL) of 0 dB re 20 µPa (often incorrectly abbreviated as 0 dB SPL). Prolonged exposure to a sound pressure level exceeding 85 dB can permanently damage the ear, sometimes resulting in tinnitus and hearing impairment. Sound levels in the hearing range, in excess of 130 dB are considered more than the human ear can withstand and may result in serious pain and permanent damage. At very high amplitudes, sound waves exhibit non-linear effects including shock.

[edit]
Speed of sound
Main article: Speed of sound
The speed at which sound travels depends on the medium through which the sound waves pass, and is often quoted as a fundamental property of the material. In general, the speed of sound is proportional to the square root of the ratio of the stiffness of the medium and its density. Those physical properties and the speed of sound change with ambient conditions. For example, the speed of sound in air and other gases depends on temperature. In air, the speed of sound is approximately 345 ms-1, in water 1500 ms-1 and in a bar of steel 5000 ms-1.

[edit]
Sound pressure
Sound pressure is the pressure deviation from the local ambient pressure caused by a sound wave. Sound pressure can be measured using a microphone in air and a hydrophone in water. The SI unit for sound pressure is the pascal (symbol: Pa). The instantaneous sound pressure is the deviation from the local ambient pressure caused by a sound wave at a given location and given instant in time. The effective sound pressure is the root mean square of the instantaneous sound pressure over a given interval of time. In a sound wave, the complementary variable to sound pressure is the acoustic particle velocity. For small amplitudes, sound pressure and particle velocity are linearly related and their ratio is the acoustic impedance. The acoustic impedance depends on both the characteristics of the wave and the medium. The local instantaneous sound intensity is the product of the sound pressure and the acoustic particle velocity and is, therefore, a vector quantity.

[edit]
Sound pressure level
As the human ear can detect sounds with a very wide range of amplitudes, sound pressure is often measured as a level on a logarithmic decibel scale.

The sound pressure level (SPL) or Lp is defined as


where p is the root-mean-square sound pressure and p0 is a reference sound pressure. (When using sound pressure levels, it is important to always quote the reference sound pressure used.) Commonly used reference sound pressures, defined in the standard ANSI S1.1-1994, are 20 µPa in air and 1 µPa in water.
Since the human ear does not have a flat spectral response, sound pressure levels are often frequency weighted so that the measured level will match perceived sound level. The International Electrotechnical Commission (IEC) has defined several weighting schemes. A-weighting attempts to match the response of the human ear to noise and A-weighted sound pressure levels are labeled dBA. C-weighting is used to measure peak sound levels.

[edit]
Examples of sound pressure and sound pressure levels
Source of sound sound pressure sound pressure level
pascal dB re 20 µPa
threshold of pain 100 134
hearing damage during short term effect 20 approx. 120
jet, 100 m distant 6 - 200 110 - 140
jack hammer, 1 m distant / discotheque 2 approx. 100
hearing damage during long-term effect 6×10−1 approx. 90
major road, 10 m distant 2×10−1 - 6×10−1 80 - 90
passenger car, 10 m distant 2×10−2 - 2×10−1 60 - 80
TV set at home level, 1 m distant 2×10−2 ca. 60
normal talking, 1 m distant 2×10−3 - 2×10−2 40 - 60
very calm room 2×10−4 - 6×10−4 20 - 30
leaves noise, calm breathing 6×10−5 10
auditory threshold at 2 kHz 2×10−5 0
[edit]
References
Beranek, Leo L, "Acoustics" (1993) Acoustical Society of America. ISBN 0-88318-494-X



[edit]
Measurement of sound
Decibel, sone, mel, phon
Sound pressure, acoustic pressure, sound pressure level
Particle velocity, acoustic velocity, sound velocity
Particle displacement, particle amplitude, particle acceleration
Sound power, acoustic power, sound power level
Sound intensity, acoustic intensity, sound intensity level
Acoustic impedance, sound impedance, characteristic impedance
Speed of sound, amplitude
Sound energy flux
See also Template:Sound measurements
[edit]
See also
Acoustics | Auditory imagery | Audio signal processing | Beats | Cycles | Decibel | Doppler Effect | Echo | Infrasound | Loudspeaker | Microphone | Music | Noise | Phonons | Physics of music | Pitch | Radiation of sound | Resonance | Rijke tube | Reflection | Reverberation | Sonic weaponry | Sound localization | Soundproofing | Sound reproduction | Steam whistle | Timbre | Tinnitus | Ultrasound | Voyager Golden Record | Wave |

Wikibooks has more about this subject:
School science how-to


[edit]
External links
Wikiquote has a collection of quotations related to:
SoundHyperPhysics: Sound and Hearing
Sounds Amazing a learning resource for sound and waves
Hearing curves and on-line hearing test
Audio calculations and online acoustics conversion engine
Retrieved from "http://en.wikipedia.org/wiki/Sound"

 

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Look, you cannot speak english and then refute the dictionary as being incorrect.

Here is the best concise definition I found which includes reference to those concerned about human involvement -

Not to say your definition isn't valid, and also in the dictionary, but this one is the most scientific and should be used in terms of describing physical reality. Notice that sound is "capable" of being detected by human organs of hearing.

Regarding light waves, and radio waves et. al., they do not change their substance when we perceive them.
The english language contains an agreement we make that a light bulb is scientifically designed to produce "light", and it produces "light" in an empty room.
What you are saying is that we create light in a room, from the raw material of light waves, when we walk into it - but this is not in accord with physics, because we make no changes to that source by oserving it.
You might as well say that we create a painting by observing it.
Or that we create a radio broadcast by listening to it ?
That is a fine mental concept, but don't pretend it is the rule when relating to linguistic and scientific understandings.

 

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Yes and with this in mind, once again note that the prefix is 'make' not 'percieve'!

 

Let's see. We're in General Philosophy. OK. I'm up for it. I can speak English and I refute the dictionary.

Therefore you are mistaken, since you said one could not do this.

Therefore, since one of your premises is flawed, your entire thesis is called into question.

I just love this philosophy. It's very similar to being drunk.

 

Very similar to being a retard too.

 

As far as I can tell, that is exactly what happens. Until I observe the painting the waveforms which constitute its existence have not collapsed. The moment I turn away it proceeds to become a complex combination of waveforms.

 

No it doesnt! the light emitted from it does, but the painting itself remains the same if you look it at not. Furthermore, the wave fuction will also collapse if it hits any other object besides an eye.

 

Prove it.

 

The tree makes a sound. By all definitions. The question is "does a tree MAKE a SOUND if it falls in the forest and there's no one around to hear it?".

Unequivocally, yes. It does.

If the question was "When a tree falls and makes a crashing sound, if no one is around to percieve it, is there still a sound?"

Of course there is.

Sound, by definition, is a specific range of frequencies of pressure disturbances in air (or solid or liquid).

I think this thread has reached a solidly satisfying conclusion.

 

The object itself is still there. Want proof? Walk into the room blindfolded. You can't see it, but you can touch it.

 

It does not make a sound. Sound requires perception. If there is nobody there to perceive, then there is no sound. Your protestations will not alter this singular fact.

 

if a lightwave of the frequecy of blue light enters a room does the room turn blue?

 

I don't need to see it to collapse its waveform, I merely need to observe it. That can be done by touch as readily as by sight.
Indeed it is only the fact that I can smell the rotteness of your argument that makes it real.

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Solipsism is satisfying.

 

Wave function collapse only applies to quantum objects and some larger groups of objects under extraordinary circumstances (bose-einstein condensates?). Macro objects are not subject to such a thing since the trillions of particles making it up all disturb or interfere with (collapse) each other continuously.

 

You do not accept the common definition of sound then?

 

no it doesn't. it produces a soundwave.
sound is what we perceive when we hear a soundwave.

does a room "lightup" if no one sees it?

 

Please recant or I shall ignore you thus turning you into a puff of quantum uncertainty.

 

Of course! The physical definition of sound or light does not require perception!!!

 

*sits down in armchair with bucket of popcorn*