Music and Sound Blog

THE SOUND

admin — Tue, 27 Jan 2009 18:19:55 +0000

The sound is the auditory perception of a physical phenomenon that consta in the possibility of means (solid, liquid or gaseous), to transmit an oscillation of own pressure.

In the air as an example the sonorous waves are generated from variations of the pressure to of over and to of under of the static value of the atmospheric pressure. Because it marks them can be transmitted means it needs having mass and elasticity, that is must have the ability to return once to the state of quiet that the sollicitation on it stops.

For these motivations the empty one is not in a position to transmitting noise. The single particles of air (or however of means), vibrate in ahead and behind, transmitting the waves but they maintain their medium position approximately unchanged.

Every solid body, liquid or gaseous possesses therefore a mass and an elasticity and is in a position to transmitting the sound; this that differs proportionally to the characteristics of mass and elasticity of means is the speed with which the sound it can be propagated.

Explanation of the Sound

admin — Tue, 27 Jan 2009 17:09:26 +0000

Our voice, the sound of an instrument, the sound of a bird is all aspects of various ones of the same phenomenon: the sound. The sound is provoked from the vibrations of an elastic body and in order propagar itself it has need of means: air; any solid, liquid or gaseous substance. The sound is provoked through of the vibrations that produce to a succession of jams and expansions of molecules dell’ air. In their oscillating movement they form the concentric spherical sonorous waves said sonorous waves that they arrive to our ear therefore the sound is produced from the vibrations of a body and is provoked through other substances under sonorous wave shape. The rappresentazione of a sonorous wave When a sonorous wave is propaga not c’ it is a transport of matter, but an oscillating motion around their position of quiet. Un’ sonorous wave can be represented with a diagram from the waved form called sinusoid. Its high part is called crest (that it corresponds to the jam) while the part lowland comes called ventre (correspondent all’ expansion). The distance between the crest or ventre and lasse the x is l’ amplitude of the sound. While the distance between two ventri or two successive crests calls length d’ wave. The movement that door to the initial state them from the crest to the quiet ones comes called complete oscillation. Speed of propagation the speed of sound is various according to the means in which the propagation happens; in fact the speed is greater in the solid bodies, smaller in the liquids and still inferior in the gas. This happens because in the solid bodies the molecules more closely are tied between they transmitting, thus, better the sonorous waves to the contrarys of the liquids and of gas since their molecules they are more and more far between they. Through to complex calculations executed for the first time in France in the 1882 the speed of sound has been settled down that nell’ air is of 340m to the second. The substance in which the sound is provoked besides to determine the speed of sound attenuates and dampens the same sound, than, gradually she becomes more and more weak person. This effect more or less is emphasized in the various substances. In fact some substances attenuate less the sound than others thus rendering the propagation better. The substances that attenuate the good ones little come called good conductors, on the contrary the substances attenuate that come said it very acoustic or fonoassorbenti insulators. The liquids, the metals, the ground and the gas are of the good conductors; on the contrary the material, the rubber, the glass, the plastic, the polistirol are acoustic insulators, the cork and the cardboard. Characters symbols of the sound the several sounds distinguish themselves in: frequency, intensity and the stamp. The frequency is the number of complete oscillations (n) that completes a sonorous wave nell’ unit time (t), that is f=n/t. It measure in Hertz (Hz) that it corresponds to a complete oscillation of a sound in a second, 1 Hz= 1 oscillation to the second

Scramjet: seven times faster of the sound

admin — Tue, 27 Jan 2009 16:57:36 +0000

Experienced in Australia the first prototype of a motor revolutionary

A new motor in a position to pushing a faster aircraft till seven times of the sound has been launch for the first time in Australia. The launch has happened from the polygon of Woomera, neighbor to Adelaide, from where the HyShot has left in top to a rocket. Unfortunately, the Australian scientists still have not been in a position to establishing if the Scramjet has really worked or not. The spokesman of the plan, Peter McCutcheon, in fact has said ” we are still analyzing the data… we are not sure, at the moment, if or be a success.” For a positive outcome of the test, they would be sufficient little of acceleration, due to the push of the Scramjet nell’ last part of the flight. The Scramjet is simple, in theory, because they do not have parts in motion and they take dall’ atmosphere l’ oxygen that serves they in order to burn the fuel. This renders them of the normal rockets, that they must carry to edge or the fuel or the comburente, adding weight more efficient. One of the problems with the Scramjet is but that they begin to only work to advanced speeds to Mach 5, or five times the speed of sound. In theory, in future these motors they could equip airplane in a position to flying in two hours dall’ Europe all’ Australia, but the road to complete before their putting to point is still long. Some month it makes also NASA had tried a similar test, failed but for a problem to the rocket that had to accelerate the prototype till an apt speed to the operation of the Scramjet.

The elaboration of the sound in the autistic ones

admin — Fri, 23 Jan 2009 21:59:39 +0000

Tenuous it marks them magnetic nell’ cerebral activity of the autistic children shows that they elaborate the sound and the language in a different way from the not autistic children. E’ how much turns out from a search lead near the Children’ s Hospital of Philadelphia and introduced to the conference anniversary of the Radiological Society of North America in course to Chicago.

LThe identification and the classification of these outlines of cerebral answer will be able to concur a more accurate diagnosis dell’ autism and to develop therapeutic approaches for the treatment of this disturbance.

” The children with autism answer more slowly with a fraction of second of the healthy contemporarys to the vocal sounds and the intonazioni” , he has said Timothy Roberts, that he has directed the search, conduct taking advantage of magnetoencefalografia (MEG), a technique already used for the study dell’ epilepsy that finds the cerebral magnetic fields own like l’ elettroencefalografia (EEG) of it finds the electric fields. ” It marks them cerebral electrical workers generate little ones you live magnetic whom they change with the feelings and the communication between the several areas of the brain”.

” Our hypothesis is that spoken and the other sounds arrive too much quickly for the children with distrurbes of the autistic phantom and that their difficulties nell’ elaboration of the sound can hinder the linguistiche performances and of comunication” , it has added Roberts.

When it comes introduced a sound, the MEG records a delay of 20 milliseconds in the cerebral answer of the subjects with disturbances of the autistic phantom regarding those normal schools. This delay indicates that the auditory process is abnormal in the autistic children and can carry to a cascade of delays and an overload of the successive processes of elaboration of the sounds and the spoken one.

Since the autism is introduced in a wide phantom of ability and disability works them, the ” firme” magnetic of the cerebral answer it could allow a more accurate diagnosis of the under type of autism of the single patients, and this also to un’ premature age, with a benefit for the timeliness of the participations.

Science of the sound

admin — Wed, 21 Jan 2009 23:30:33 +0000

Between the 1895 and 1915 Wallace Clement Sabine, Hollis University professor of Mathematics and Philosophy all’ University of Harvard, threw the foundations of a new science, l’ architectonic acoustics. Before Sabine, in the architectonic planning it was limited to us to imitate knows them to them in which l’ acoustic good era. Moreover they were in vigor a series of practical superstizion, like that to stretch of the useless threads in the high parts of churches or knows them from concert. L’ architectonic acoustics were born because a remarkable man found itself of forehead to a situation that demanded a solution: the problem consisted in the fact that was nearly impossible to understand the lecturers in knows it of the Fogg Art Museum, that it had been hardly opened. In 1895, l’ University of Harvard churches to Sabine to find a remedy. Sabine approached the problems dell’ architectonic acoustics fortified of an acute and indagatrice mind, a good ear, a chronometer, an organ to canes with a compressed air tank like sonorous source. It identified the reason for which the speeches in know it of the Fogg Art Museum were inintelligibili: the sound too much persisted over a long time span (that is the riverberazion was excessive). Sabine reduced the riverberazion covering of felt some walls. After that, it wrote, knows it divenne ” not excellent, but completely apt to the scope”.

Sabine was the first one to define the time of riverberazione, a parameter a lot important in the study dell’ acoustics of know them from concert. According to the definition of Sabine, this was the time employed from a reverberating sound in order to become hardly audible. Many years after, when divenne possible to execute electronic measurements of the level of sonorous intensity, the time of riverberazion came defined like the time employed from a sound, after its extinction, in order to decrease of 60 dB of level of intensity; this is the accepted definition today. Various musics and theatres demand different times of riverberazione. One of the greater problems dell’ architectonic acoustics always have been that one to obtain of the accurate calculations of the times of riverberazione. Sabine not only defined the time of riverberazion, but it invented also a useful way, even if not completely precise, in order according to calculate it the volume and of the fraction of the sound incident reflected from the walls and the other superficial ones.

The job of Sabine was arduous. Working in a room basement with concrete walls and fire-bricks it succeeded to measure the coefficients of absorption of many various materials. In other places, Sabine passed entire nights waiting for of the sufficiently silent moments for being able to execute its measurements. It studied also the transmission of the sound and the way in order to isolate the rooms acoustic, a felt necessity a lot in the conservatives. Sabine was above all dedicated to improve l’ acoustics of know planned them from architects who were totally all’ dark of the necessities of the listeners or that simply they were not cured any: a defect still much municipality between the architects. But Sabine planned also one knows it, the Symphony Hall di Boston, constructed in 1900. Still today the Symphony Hall is one of the best ones knows them from concert of the world.

The history of Wallace Sabine is the history of the triumph of a new scientific discipline.

Recently they have been made ulterior progresses in the theory of the time of riverberazione. For many years the ” was known that; corretto” approach was given from un’ integral equation much complicating; such equation is essentially irresolubile, also to the computer. And. N. Gilbert has recently shown that using un’ other integral equation era in a position to obtaining turned out valid with a iterativo method. Gilbert has thus obtained of the result ” corretti” for several forms sluices. The calculations and the measures of physical amounts which the time of interesting riverberazione are a lot. In 1967, Manfred Schroeder and Bishnu Atal they showed as two loudspeakers can produce a placed sonorous source externally appearing to the two loudspeakers. In 1969, P. Damaske and V. Mellert they used this effect in order to produce to a system stereo ” perfetto”. The sounds came collected from two auditivi culverts of a head fortified feint of two auricular pavilions. It marks them came then leaked, elaborated and sent to two loudspeakers situated in an anechoic chamber.

The sounds emitted from the two loudspeakers could exactly recreate in the auditivi culverts of the head feint the same sollicitations of sonorous pressure that had been taken when the head was exposed to the recording from the alive one. Schroeder and its two collaborators, D. Gottlob and K.F. Siebrasse, confronted more than twenty know them from concert European. They succeeded to obtain a recording of sinfonia the Jupiter di executed Mozart dall’ orchestra of the BBC in an anechoic chamber. Schroeder, Gottlob and Siebrasse played this recording using several loudspeakers placed on the stages of the various ones know taken them in consideration. In ciascuna it knows recorded it what the head feint felt when was seated in various positions and with these recordings they could then recreate in to anechoic chamber exactly what the head feint had felt in the several ones knows them.

Work in JJCAAS.org

admin — Wed, 21 Jan 2009 03:54:45 +0000

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JJCAAS 2009

admin — Wed, 21 Jan 2009 03:32:47 +0000

JJCAAS 2009 is a new Meeting of Young Researchers in Audition, Musical
Acoustics and Audio Signal. The goal of this meeting is to enable
communication between PhD students whose fields of investigation share
common interest. The JJCAAS favor therefore current and future
scientific collaborations. Young researchers are thus given the occasion
to increase the value of their studies by presenting them to their
peers.