Desciribing intensity of human scream?

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    Human Intensity
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Discussion Overview

The discussion revolves around the intensity of a human scream, specifically examining the claim that the energy produced by screaming for a prolonged period could warm a cup of coffee. Participants explore the relationship between sound intensity measured in decibels and the power output of a scream, considering factors such as the area of the mouth opening and the definitions of sound measurements.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether the area of the mouth opening should be considered when calculating the power of a scream, noting a discrepancy in an article that does not account for it.
  • Another participant argues that the article does take the area into account, suggesting that the intensity of 80 dB corresponds to a power output of approximately 0.001 watts, but questions the assumed area of 10 m² as being too large.
  • It is noted that the intensity of sound can vary based on distance and directionality, with one participant clarifying that decibels measure sound power level (SPL) rather than perceived loudness.
  • Participants discuss the confusion around the use of watts versus watts per square meter in the context of the article, indicating a lack of clarity in the definitions used.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of sound intensity measurements and the relevance of mouth area in calculations. There is no consensus on the correct approach to the problem, and the discussion remains unresolved regarding the implications of these factors.

Contextual Notes

Participants highlight limitations in the clarity of definitions used in the referenced article, particularly concerning the distinction between sound power and sound intensity. There are unresolved assumptions regarding the area of the mouth and its impact on the calculations.

utkarsh5
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i was trying to verify the '8 years 7 months 6 days' myth/fact that states that you would have you scream for that much time to produce enough energy to warm up a cup of coffee. i assume that an average human screams at 80 dB.if i have to calculate the power,do i have to take the area of mouth opening into account?i think i do,but in the following article,the person who answered the question did not take it into account(or as it seems).

http://www.physicscentral.com/explore/poster-coffee.cfm

please answer.any help would be greatly appreciated.
 
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in the following article,the person who answered the question did not take [area of mouth opening] into account
It appears the author did - from the article cited:
80 decibels produces .001 watts of energy(sic)
... the intensity from the sound would be in watts per square meter.

80dB would be about 1x10-4Wm-2 ... so he seems to have used an area of about 10m2 ... which seems a little large. Perhaps the author has a big mouth?

The whole thing is suspect isn't it - I'm sure I can make myself heard in the front rows of a rock concert - well, by yelling in someone's ear.
If I yell at a cup of coffee the same intensity that is more like 0.1Wm-2. Figure a mouth area of about a square decimeter
(0.1m x 0.1m = 0.01m-2) and that's 0.001W directed at the cup.

So the final figure is about right.

ref. http://www.physicsclassroom.com/class/sound/u11l2b.cfm
 
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"Decibels" are used to measure serveral different quantities. Your link seems to be talking about "sound power level" (SPL) whcih measures the total acoustic power that the sound source (i.e. the scream) generates. That is not the same as "how loud the scream sounds" which depends how far away from the source you are, and the fact that the sound may be directional.

1 dB SPL is arbitrarily defined as ##10^{-12}## watts of acoustic power, so 80 dB SPL = 0.0001 W

Assuming 80db is the right SPL, your link gives the time if you can somehow capture all the power from the scream and use it to heat the coffee.

Edit: I was writing this when Simon Birdge posted, but note that SPL is measured in watts, not in watts/meter^2. The OP's link isn't very clear exactly what it means by "decibels", though.
 
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@AlephZero: yes, I noticed that too.
The author could just be using a different scale to me.
 
thanks for the replies!what confused me was exactly that the author had not used watts/(meter^2),and had used just watts.that was pretty strange.anyways,thanks for the clarification! :D
 

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