Frequency of the sound of scratching Nails on Chalkboard

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In order to get my question , first read this please,

Michael Oehler of the Macromedia University for Media and Communication and University of Vienna's Christoph Reuter, whose new research into the unpleasant sound may have found the root of our dislike.

In their research, the two musicologists looked at both physical and psychological reactions to unpleasant sounds.

The most impressive results came in the physiological measurements taken by the researchers. They found a dramatic change in skin conductivity when unpleasant sounds were played, showing a distinct physical reaction to the sound. The researchers also pinned down the frequency range of skin-crawling sound to between 2,000 and 4,000 Hz — which is the same range as human speech. Amazingly, when these frequencies were filtered out and the sound replayed, participants had no trouble listening to the sound.

The range of frequencies for unpleasant sounds is also important because of the structure of human ears. Our ears are shaped in such a way that they amplify frequencies between 2,000 to 4,000 Hz. The researchers believe that the chalkboard sound, and similar tones, are unbearable because the amplification is so great to the point that it becomes painful.
So it means that when the sound is produced from nails on the chalkboard, the frequency range of this sound is between 2,000HZ to 4,000HZ with the amplitude of the sound is mostly a noise ? and human ears are designed to amplify this range of frequency, which is why the sound is unpleasant to our ears ?

If that is true, and every human has its ear designed to amplify sound ranges from 2,000Hz to 4000Hz frequency then why such sounds isn't unpleasant to everyone ? Does it mean that not every ear is capable of amplify these frequency or every ear is trained to amplify the range of the frequency according to the environment they have grown from their birth ?

There are certain other sound which specifically unpleasant to some people and other sounds to other people like when we try to cut the silk yarn or silk cloth from our teeth and it slips out from our teeth the sound which is produce is highly unpleasant to some of the people. Another example is the sound of any pointed tip tool on the zigzag surface.

These sounds are not unpleasant to everyone rather it is unpleasant to some of the people. If every ear amplify the same frequency range of 2,000Hz to 4,000Hz and if these sounds are mostly the noise then why these sounds with noises doesn't affect everyone's ear ?
 

davenn

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for the same reason some various people like or dislike anything, say a particular type of food, a smell ( scent) etc.
You would have to start looking at the psychological reasons as to why one person likes or dislikes something compared to another person

that would be one of my initial thoughts

Dave
 

Bobbywhy

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Scraping a chalkboard with the fingernails produces a sound which most people find unpleasant. The basis of this innate reaction has been studied in the field of psychoacoustics.
http://en.wikipedia.org/wiki/Sound_of_fingernails_scraping_chalkboard

ASA Lay Language Papers
162nd Acoustical Society of America Meeting
“Psychoacoustics of chalkboard squeaking”
“Based on these findings, it can be said that the relevant acoustic characteristics of unpleasant sounds can be found in the pitch information and in the frequency range between 2000 Hz and 4000 Hz, where the ear is most sensitive. Such (unpleasant) sounds seem to evoke a physical reaction in the listener—in other words, the galvanic skin response changes significantly, and in addition, knowledge about the origins of the sounds (e.g., scratching fingernails on a chalkboard) leads to more negative ratings and stronger physiological effects.”
http://www.acoustics.org/press/162nd/Oehler_4pPP6.html [Broken]
 
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Just thinking of that sound gives me goose bumbs. I don't even have to hear it.
 
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babies scream at avarage around 3khz. Evolution.
 

Bobbywhy

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“Scraping sounds and disgusting noises”
Trevor J. Cox, Acoustics Research Centre, University of Salford, Salford M5 4WT, UK

Abstract
Thirty-four horrible sounds have been examined in an Internet-based psychoacoustic experiment. This paper presents the results for the scraping and disgusting noises used. It is not understood why some humans find certain scraping noises, such as the sound of fingernails being scraped down a blackboard, so terrible. In this experiment, the variations in ratings with age, gender and location are examined. The results for one of the scraping sounds is consistent with the hypothesis suggested by others, that the response comes from a vestigial reflex related to the warning cries of monkeys. But this was not true for the actual recording of the fingernails scraping down a blackboard.

An alternative hypothesis that the response is related to an audio–haptic interaction was tested and results indicated that this idea warrants further investigation. Other possible causes of the response, drawing on work concerning dissonance, are tentatively suggested. The disgusting sounds examined included the worst sound found in the experiment, the sound of someone vomiting. However, none of the disgusting sounds tested promoted responses consistent with a ‘disgust reaction’ based purely on survival instincts. Cultural factors might be important in our response to the disgusting sounds, with the influence of manners and etiquette being suggested as a possible factor.

Rank Sound Title
1Vomiting
2 Microphone Feedback
3* Multiple Babies Crying
3* Scrape of Train Wheels
5 Squeak of Seesaw
6 Violin Played Badly
7* Whoopee cushion
7* Single Baby Crying
9* Soap Opera Argument
9* Mains hum
11 Tasmanian Devil
12* Cough
12* Cat Spitting and Howling
12* Mobile Phone Ringing
15 Creaky Door
16* Barking Mad Dog
16* Sniff
16* Fingernails on a Blackboard
16* Polystyrene
20 Dentists' Drill
21 Cough and Spit
22 Alarm Clock
23 Fast Electrical Drilling
24 Apple Munch
25 Creaky Stairs
26* Squeaky Trolley
26* Snoring
28* Electrical Throb
28* Cat Eating Noisily
30 Reverberated Whoopee Cushion
31 Aircraft Take-off
32 Drums
33 Gong
34 Low, Not-Quite-Eerie Noise
(* signifies a tie)
http://dx.doi.org/10.1016/j.apacoust.2007.11.004 [Broken], How to Cite or Link Using DOI
 
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Bobbywhy

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Saccular Acoustic Sensitivity, From Wikipedia, the free encyclopedia

“Saccular Acoustic Sensitivity is a measurement of the ear's affectability to sound. The saccule's normal function is to keep the body balanced, but it is believed to have some hearing function for special frequencies and tones. Saccular acoustic sensitivity is considered to be simply an extension of the sense of hearing through the use of the saccule.

Effects
Saccular acoustic sensitivity has a variety physiological as well as mental/emotional effects.

Physical Effects
Perhaps the most observable physical response is goose bumps. A similar effect is the manifestation of chills. Some sounds have been known to cause reflexive muscle movements like a twitch or even a jump.[1] Since these physical effects are easily recorded and are linked consistently with strong emotion, they have been used in several types of psychological studies.[2]

Mental/Emotional Effects
Certain sounds, such as fingernails drawn down a blackboard, cause strong feelings of aversion or even fear in most humans. A 2004 study claimed that the blackboard sound was very similar to the warning cry of Siamang gibbons and hypothesized that a vestigial reflex is what causes the fight or flight reaction in humans.[3] Other sounds, such as a person coughing or vomiting, provoke responses of disgust. These emotional reactions are thought to be caused by the body's natural tendency to avoid disease.[4]

Stimulation Negative Stimulation
While each individual is sensitive to different sounds, there are some nearly universal saccular acoustical stimulants. For example, the sound of fingernails scratching a blackboard will stimulate negative emotions along with chills in the majority of the population. Trevor J. Cox, of the University of Salford, was fascinated by this fact and conducted an online study to identify the "most horrible sound" in the world. Participants were asked to listen to recordings of various "bad" noises and rate them by their horribleness. "Vomiting" was selected as the most horrible sound by a wide margin. Surprisingly, "nails on a blackboard" was only ranked 16.[5]

Positive Stimulation
There are various sounds that correspond to positive physical and emotional reactions as well. Therapists use these soothing sounds for therapy in stress relief and relaxation. However, most of the sounds that invoke positive responses tend to be more subjective. Familiarity tends to play a large role in the amount of positive stimulation observed. For example, a man listening to a familiar song is more likely to experience pleasure and have goosebumps than a man listening to an unfamiliar song.[6]

http://en.wikipedia.org/wiki/Saccular_Acoustic_Sensitivity
 
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Ok, I like psychoacoustics so I'm glad I clicked on this. It is true that human perception of loudness is not linear with frequency lower frequencies are far less perceptible for example and a tone of 40Hz at 80dB will be the same 'loudness' as a 1kHz tone at 50dB. The peak at around 4kHz is due to the resonant character of the outer ear. Obviously this is not absolutely the same for everyone and is only an average over a massive group of people and individual values will vary, although not by a lot (look up fletcher-munson curves).

As for why, my guess is (as someone postulated above) evolution... Babies cry at about 3-4kHz, bushes rustle and twigs snap at about that frequency the generations previous probably thrived if they knew when their child was un rested or could hear potential foes approaching. This is why we hate the sound of vomit (thanks trevor cox) generally 'back in the day' you would eat the same food as your other tribe members, if they get ill you will probably be ill, so vomiting as a reaction to hearing someone vomit makes sense.

Sounds may become annoying because they are loud but not all loud sounds are annoying and just audible sounds can be very annoying so its not just about amplitude. Fastl and Zwicker have shown that intermittent noise or pulsations at particular rates and various other factors will increase annoyance.

The reason it will not have the same effect on everyone is simply because we are not all the same, we all have different thresholds of pain, tolerance and hearing etc.. I think that answered your question. If not, let me know.

Ben.
 
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