# Perception of sound  (Page 2/3)

 Page 2 / 3

The screencast video of illustrates two different approaches to this problem, and demonstrates the perceptual effects that result from treating pitch perception as linear instead of logarithmic.

## Intensity and amplitude

Perception of sound intensity also logarithmic. When you judge one sound to be twice as loud as another, you actually perceive the ratio of the two sound intensities. For example, consider the case of two people talking with one another. You may decide that one person talks twice as loud as the other, and then measure the acoustic power emanating from each person; call these two measurements ${T}_{1}$ and ${T}_{2}$ . Next, suppose that you are near an airport runway, and decide that the engine noise of one aircraft is twice the intensity of another aircraft (you also measure these intensities as ${A}_{1}$ and ${A}_{2}$ ). In terms of acoustic intensity, the difference between the talkers ${T}_{2}-{T}_{1}$ is negligible compared to the enormous difference in acoustic intensity ${A}_{2}-{A}_{1}$ . However, the ratios ${T}_{2}/{T}_{1}$ and ${A}_{2}/{A}_{1}$ would be identical.

The decibel (abbreviated dB ) is normally used to describe ratios of acoustic intensity. The decibel is defined in :

${R}_{\text{dB}}=10{\mathrm{log}}_{10}\left(\frac{{I}_{2}}{{I}_{1}}\right)$

where ${I}_{1}$ and ${I}_{2}$ represent two acoustic intensities to be compared, and ${R}_{\text{dB}}$ denotes the ratio of the two intensities.

Acoustic intensity measures power per unit area, with a unit of watts per square meter. The operative word here is power . When designing or manipulating audio signals, you normally think in terms of amplitude , however. The power of a signal is proportional to the square of its amplitude. Therefore, when considering the ratios of two amplitudes ${A}_{1}$ and ${A}_{2}$ , the ratio in decibels is defined as in :

${R}_{\text{dB}}=20{\mathrm{log}}_{10}\left(\frac{{A}_{2}}{{A}_{1}}\right)$

Can you explain why "10" becomes "20"? Recall that $\mathrm{log}\left({a}^{b}\right)=b\mathrm{log}\left(a\right)$ .

Often it is desirable to synthesize an audio signal so that its perceived intensity will follow a specific trajectory . For example, suppose that the intensity should begin at silence, gradually increase to a maximum value, and then gradually decrease back to silence. Furthermore, suppose that you should perceive a uniform rate of change in intensity.

The screencast video of illustrates two different approaches to this problem, and demonstrates the perceptual effects that result from treating intensity perception as linear instead of logarithmic.

## Harmonics and overtones

Musical instruments produce sound composed of a fundamental frequency and harmonics or overtones . The relative strength and number of harmonics produced by an instrument is called timbre , a property that allows the listener to distinguish between a violin, an oboe, and a trumpet that all sound the same pitch. See Timbre: The Color of Music for further discussion.

You perhaps have studied the concept of Fourier series, which states that any periodic signal can be expressed as a sum of sinusoids, where each sinusoid is an exact integer multiple of the fundamental frequency; refer to :

what are the products of Nano chemistry?
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
Preparation and Applications of Nanomaterial for Drug Delivery
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
I only see partial conversation and what's the question here!
what about nanotechnology for water purification
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
what is the stm
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
why we need to study biomolecules, molecular biology in nanotechnology?
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
why?
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
research.net
kanaga
sciencedirect big data base
Ernesto
Got questions? Join the online conversation and get instant answers!