ATRAC: Adaptive Transform Acoustic Coding for MiniDisc
Abstract
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ATRAC is an audio coding system based on psychoacoustic principles.
The input signal is divided into three subbands which are then
transformed into the frequency domain using a variable block length.
Transform coefficients are grouped into nonuniform bands to reflect
the human auditory system, and then quantized on the basis of dynamic
sensitivity and masking characteristics. ATRAC compresses compact disc
audio to approximately 1/5 of the original data rate with virtually no
loss in sound quality.
1 Introduction
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Recently, there has been an increasing consumer demand for a portable
recordable high-quality digital audio media. The MiniDisc system was
developed to meet this demand. The MiniDisc is based on a 64 mm
optical or magneto-optical disc which has approximately 1/5 of the
data storage capacity of a standard compact disc. Despite the reduced
storage capacity, it was necessary that the MiniDisc maintain high
sound quality and a playing time of 74 minutes. The ATRAC (Adaptive
Transform Acoustic Coding) data compression system was therefor
designed to meet the following criteria:
* Compression of 16-bit 44.1 kHz stereo audio into less than 1/5 of
the original data rate with minimal reduction in sound quality.
* Simple and inexpensive hardware implementation suitable for
portable players and recorders.
When digital audio data is compressed, there is normally a certain
amount of quantization noise introduced into the signal. The goal of
many audio coding systems [1-6] is to control the time-frequency
distribution of this noise in such a way as to render it inaudible to
the human ear. If this is completely successful, the reconstructed
signal will be indistinguishable from the original.
In general, audio coders operate by decomposing the signal into a set
of units, each corresponding to a certain range in time and frequency.
Using this time-frequency distribution, the signal is analyzed
according to psychoacoustic principles.
This is a written report where my partner on the topic and I presented a ten minute oral summary of our chosen research topic on Technicolor. We chose Technicolor as we felt it had most to say to us, threw the progression of the technology the problems threw out the years of perfecting the technology, to the ultimate glory of the Technicolor experience.
Anderson, Rick. "Johann Adolf Hasse. (Sound Recording Reviews)." Notes 58.4 (2002): 902. Academic OneFile. Web. 14 Mar. 2014.
I am going to explain the basic concepts of subtractive synthesis and the terminology of subtractive synthesisers with reference to acoustic principles.
The movie that I watched is named Sound and Fury. The movie follows the Artinian family, which is distinguished by two brothers. One brother, Peter, is Deaf and has a Deaf wife and three Deaf children, one of which is Heather, the focus of the documentary. The other brother is Chris, who is hearing, along with his hearing wife, Mari, and their twin sons. One son is hearing and other one, named Peter, is deaf. The family is at odds over the debate of cochlear implants. A cochlear implant is a surgically-implanted device for profoundly deaf or severely hard-of-hearing individuals. It provides the individual with a sense of sound by stimulating the cochlear nerve. A situation arises when Heather wants to have a cochlear implant and her parents do not really understand why.
Specific Purpose: To help people to understand what Audism is and that the lack of an ability to hear does not mean they are incapable of performing tasks.
Steven Connor delves into the mixing and creating of sound by computerisation, as well as the habits of sound; it’s immersion, pathos and objectivity.
compression ratio and CD- quality sound. An Mp3 file compresses a sound file to one-twelfth its
Lynn Kolofske visited the Costco Hearing Aid Center 4 years ago complaining of difficulty hearing and understanding speech. Once tested I discovered an asymmetrical hearing loss. Lynn had a 55.8% pure tone average on the left ear and a 15% PTA on the right ear. Due to the difference between ears I sent Lynn out with a medical referral before discussing hearing aids. After seeing an ENT Lynn was diagnosed with an Acoustic Neuroma with surgery being the only treatment available.
3. Variable-Speech Control Tape Recorder: This is similar to any generic tape recorder, and can be found in most electronics stores. The component that is benef...
Rumsey, Francis, Time McCormick. Sound and Recording, an Introduction . Woburn , MA : Focal Press, 2002.
National Institute on Deafness and Other Communication Disorders. (November 2002). Retrieved October 17, 2004, from http://www.nidcd.nih.gov/health/hearing/coch.asp
Recording technology wasn’t always a digital process. Before the 1970s, all recordings depended on capturing a physical analogue sound with microphones. This was done on either tape or disk. Analogue recordings lacked the sonic integrity that the 21st century demanded; it was becoming increasingly problematic and expensive in reducing noise and distortion that plagued analogue recordings. As a result, audio researchers began to study digital conversion techniques. They discovered that digitizing an electrical audio signal consisted of sampling the audio wave thousands of times a second, measuring the peak amplitude of each sample, and then assigning one of a limited number of binary values to each.
Auditory localization is the ability to recognize the location from which a sound is emanating (Goldstine, 2002). There are many practical reasons for studying auditory localization. For example, previous research states that visual cues are necessary in locating a particular sound (Culling, 2000). However, blind people do not have the luxury of sight to help them locate a sound. Therefore, the ability to locate sound based only on auditory ability is important. It is also important to study different auditory processes. For example, when studying a way for a blind person to maneuver through an environment, it is helpful to know that people can most accurately locate sounds that happen directly in front of them; sounds that are far off, to the side, or behind the head are the least likely to be properly located (Goldstein, 2002).
Understanding transducer theory as well as function is vital in performing clinical ultrasound tests on patients. A transducer can be defined as any device that converts one form of energy into another. Transducers are not just something used in the ultrasound world. There are many different kinds of transducers in the world. Some examples of transducers that we come in contact with in the real world are microphones, speakers, lasers etc. (Miele).
In paper [5] Modified Discrete Cosine Transform is used in Psychoacoustic model for the perception of audio quality. In paper [3, 11] MDCT is widely used in audio coders due to the property of perfect reconstruction with critical sampling mostly with sine window. In both the papers analysis of audio signals are done using MDCT and exact results was discussed. It is not suitable for spectral analysis for several causes: it vectors are not shift-invariant, it does not conserve energy, and it cannot be understood by means of magnitude and phase [13]. Various window functions are used in practice for MDCT [11, 12]. Using adjustable window the main lobe width can be increased by reducing the side lobe. For audio signal analysis and processing mostly sine window or Kaiser Bessel Derived (KBD) window are used. Certainly, Hamming or Hanning Window is used for spectral analysis and