Completed by 9th grade students
Head Tarasova Irina Nikolaevna
Sound is a wave with a continuously changing amplitude and frequency.
A person perceives sound waves with the help of hearing in the form of sound of various volume And tones. The greater the amplitude of the sound wave, the louder the sound, the greater the frequency of oscillation, the higher the tone of the sound.
SOUND WAVE
Amplitude
high loud sound
low quiet sound
The human ear perceives sound with a frequency of 20 vibrations.
per second (low sound) up to 20,000 vibrations per second (high sound).
A person can perceive sound in a huge range of amplitudes, in which the maximum amplitude is 10 times greater than the minimum.
(100 thousand billion times). The decibel (dB) unit is used to measure sound volume. A decrease or increase in sound volume by 10 dB corresponds to a decrease or increase in sound amplitude by 10 times.
14
Sound
Loudness, dB
Lower limit of sensitivity of the human ear
0
rustle of leaves
10
Talk
60
car horn
90
Jet engine
120
pain threshold
140
Temporal sampling is the CONVERSION of a continuous audio signal into a digital discrete form.
A continuous sound wave is divided into separate small time sections, and for each such section, a certain level volume.
Audio sampling rate -
is the number of loudness measurements
sound in one second
A microphone connected to the sound card is used to record analog audio and convert it to digital form.
The quality of the received digital sound depends on the number of measurements of the sound volume per unit of time, i.e. sample rate. The more measurements are made in one second (the higher the sampling rate), the more accurately the "ladder" of the digital audio signal repeats the curve of the analog signal .
Encoding depth
Audio encoding depth is the amount of information that is needed to
Coding discrete volume levels of digital audio.
If the encoding depth is 16 bits
N is the number of volume levels
And then each volume level is assigned its own 16-bit binary code
sound e editors .
Sound editors allow you to record, play, edit sound.
Digitized sound is presented in sound editors in a visual form, so the operation of copying, moving and deleting parts of an audio track can be easily performed using the mouse.
Sound editors allow you to change the quality of digital audio by changing the sampling rate and encoding depth.
Digitized audio can be saved uncompressed in audio files in a universal format wav, as well as in compressed format MP3 .
slide 1
Coding and processing of sound information Belyaeva Zoya Viktorovna, teacher of computer science, Novouralskaya secondary school Belyaeva Zoya Viktorovnaslide 2
Sound is a wave with a continuously changing amplitude and frequency. Humans perceive sound waves with the help of hearing in the form of sound of varying volume and tone. The greater the amplitude of the sound wave, the louder the sound. The higher the oscillation frequency, the higher the tone of the sound. Belyaeva Zoya Viktorovna, computer science teacher, Novouralskaya secondary school Amplitude Time High loud sound Low quiet sound
slide 3
To measure sound loudness, a special unit is used - decibel (dB) Belyaeva Zoya Viktorovna, computer science teacher of the Novouralskaya secondary school Sound Loudness, dB Lower limit of human ear sensitivity 0 Rustle of leaves 10 Conversation 60 Car horn 90 Jet engine 120 Pain threshold 140
slide 4
In order for a computer to process sound, a continuous audio signal must be converted into discrete digital form using time sampling. A continuous sound wave is broken up into separate small time sections. A certain volume level is set for each section. Belyaeva Zoya Viktorovna, teacher of computer science, Novouralskaya secondary school
slide 5
Characteristics of digitized audio Sampling frequency (M) is the number of loudness measurements in one second. Measured in Hz (Hertz) and ranging from 8000 to 48000 Hz (8 kHz - 48 kHz) Encoding depth (i) is the amount of information needed to encode discrete digital audio loudness levels. Measured in bits. Modern sound cards provide 16-bit audio encoding depth. Belyaeva Zoya Viktorovna, teacher of computer science, Novouralskaya secondary school
slide 6
Quality of the digitized sound The quality depends on the frequency and sampling depth. Low quality: telephone communication (i = 8 bits, M = 8 kHz) High quality: audio CD (i = 16 bits, M = 48 kHz) The higher the quality, the higher the volume sound file Belyaeva Zoya Viktorovna, teacher of computer science, Novouralskaya secondary school
Coding of graphic information. No. Questions. 1. Spatial discretization is. 2. Screen resolution in graphics mode is determined by the number. 3. A page of video memory is 16,000 bytes. The display works in 320x400 pixels mode. How many colors are in the palette? 4. Determine the color depth in graphics mode, in which the palette consists of 256 colors. 5. A 256-color drawing contains 120 bytes of information. How many dots does it have? 6. Determine the number of colors in the palette at a color depth of 16 bits. 7. Black and white raster image has a size of 10 X 10 pixels. How much memory will this image take? 8. Color (with a palette of 256 colors) raster image has a size of 10 X 10 pixels. How much memory will this image take? 9. In the process of converting a raster graphic image, the number of colors decreased from 65536 to 16. How many times will the amount of memory occupied by it decrease?
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Slides captions:
Properties: sound - longitudinal wave; spreads in elastic media (air, water, various metals, etc.); has a finite speed. Sound vibrations (waves) are mechanical vibrations whose frequency ranges from 20 to 20,000 Hz. Sound vibrations 20 Hz 20,000 Hz
the loudness of the sound depends on the amplitude of the vibrations. The larger the vibration amplitude, the louder the sound. The pitch of the sound is determined by the frequency of the vibrations in the air. the speed of sound is the speed of wave propagation in the medium. sound timbre - sound coloring depending on the sound source (violin, piano, guitar, etc.). The unit of sound loudness is the decibel (dB) (a tenth of a bela). Named after Alexander Graham Bell, inventor of the telephone. sound_high_low.swf sound_quiet_aloud.swf
fourth.swf third.swf Dependence of the volume and pitch of the sound on the intensity and frequency of the sound wave
Sound source Level (dB) Calm breathing Not perceptible Whispering 10 Rustling of leaves 17 Leafing through newspapers 20 Normal house noise 40 Surf on the beach 40 Medium conversation 50 Loud conversation 70 Vacuum cleaner 80 Subway train 80 Rock concert 100 Thunder 110 Reactive engine 110 Cannon shot 120 Pain threshold 120
Audio information 2. Audio temporal scoring 3. Sampling frequency 4. Audio coding depth 5. Digitized audio quality 6. Sound editors
Analog Discrete physical quantity takes on an infinite number of values, and they change continuously. a physical quantity takes on a finite set of values, and they change stepwise. Vinyl record ( soundtrack changes its shape continuously) Audio CD (soundtrack contains areas with different reflectivity)
t A(t) Temporal sampling is the division of a continuous sound wave into separate small time sections, and a certain amplitude value is set for each section.
QUANTIZATION - the process of replacing real signal values with approximate ones with a certain accuracy. BITREYT (bitrate) - the level of quantization, the amount of information per unit of time (bits per second). That is, how much information about each second of the recording we can spend. Measured in bits (bit).
Audio information is stored as amplitude values taken at specific times (i.e. measurements are taken in "pulses").
To digitize sound, special devices are used: an analog-to-digital converter (ADC) and a digital-to-analog converter (DAC).
Let the sound encoding depth be 16 bits, then the number of sound volume levels is: N = 2 I = 2 16 = 65 536 - 1111111111111111. AUDIO SAMPLING DEPTH (I) is the amount of information needed to encode discrete digital sound volume levels. N - number of volume levels I - coding depth
AUDIO SAMPLING FREQUENCY is the number of measurements of sound volume in one second. 1 Hz = 1 / s 1 kHz = 1000 / s Samplerate (samplerate) - sampling rate (or sampling frequency) - the sampling rate of a signal continuous in time during its sampling (in particular, by an analog-to-digital converter - ADC). sound_frequency.swf
The higher the quality of digital sound, the greater the information volume of the sound file. Parameter Encoding depth Sampling frequency Telephone communications 8 bit to 8 kHz Medium quality 8 bit or 16 bit 8-48 kHz CD sound 16 bit to 48 kHz
V = I * M * t * k V - audio file volume, I - audio encoding depth, M - audio sampling frequency, t - file audio duration, k - number of audio channels (mono mode k = 1, stereo k = 2)
Example. Estimate the information volume of a high-quality stereo audio file with a duration of 1 minute, if the "depth" of encoding is 16 bits, and the sampling frequency is 48 kHz. The information volume of a sound file with a duration of 1 second is: 16 bits * 48,000 * 2 = 1,536,000 bits = 187.5 KB This means that the bit rate or playback speed should be 187.5 kilobytes per second. The information volume of a sound file with a duration of 1 minute is: 187.5 Kb / s * 60 s = 11 Mb
Noise Removal Splitting a stereo recording into two different files: Audio mixing Applying effects Sound editing is any kind of transformation.
Sound editors allow you to change the quality of digital audio and the size of the audio file by changing the sampling rate and encoding depth. Digitized audio can be saved uncompressed as universal WAV or compressed MP3 audio files. When saving sound in compressed formats, sound frequencies with low intensity that are "excessive" for human perception and coincide in time with sound frequencies with high intensity are discarded. The use of this format allows you to compress audio files dozens of times, but leads to irreversible loss of information (files cannot be restored in their original form).
WAVE (.wav) is the most widely used format. Used in Windows to store sound files. MPEG-3 (.mp3) is the most popular audio file format today. MIDI (.mid) - do not contain the sound itself, but only commands for playing the sound. The sound is synthesized using FM or WT synthesis. Real Audio (.ra, .ram) - designed to play sound on the Internet in real time. MOD (.mod) is a music format that stores digitized sound samples that can then be used as templates for individual notes.
Editing area Timeline Main menu Toolbars http://www.audacity.ru/p1aa1.html
Learn the abstract, solve problems in the notebook. Audio Coding Tasks Level 5 Determine the length of an audio file that will fit on a 3.5” floppy disk. Please note that 2847 sectors of 512 bytes are allocated for data storage on such a diskette. a) with low sound quality: mono, 8 bits, 8 kHz; b) when high quality sound: stereo, 16 bit, 48 kHz. Level "4" The user has a memory of 2.6 MB. You need to record a digital audio file with a duration of 1 minute. What should be the sampling rate and bit depth? Level 3 Specify the amount of storage space for a digital audio file that has a playing time of two minutes at a sampling rate of 44.1 kHz and a resolution of 16 bits.