It actually has three levels:
The first layer is hardware, which mainly refers to the host computer and network communication equipment used for data storage, processing and transmission;
The second layer refers to software, including all kinds of software that can be used to collect, store, retrieve, analyze, apply and evaluate information. Including ERP (enterprise resource planning), CRM (customer relationship management), SCM (supply chain management) and other business management software, as well as WF (workflow) management software for strengthening process management and DW/DM (auxiliary analysis).
The third layer refers to the application, which refers to the collection, storage, retrieval, analysis, application and evaluation of all kinds of information, including the application of ERP, CRM, SCM and other software to directly assist decision-making, and also including the use of other decision-making analysis models or the use of DW/DM and other technical means to further improve the analysis quality and assist decision-makers to make decisions (to emphasize one point, it only assists rather than replaces people's decisions).
Some people understand that it combines the first two layers into one, refers to the storage, processing and transmission of information, and the latter is the application of information; Some people combine the last two layers into one, which is divided into hard front and soft back.
Unfortunately, he often confuses the concepts of IT: one refers to the host network and the other refers to software.
What is the relationship between Microsoft's salary method and the characteristics of it industry? Just because I don't talk about some things and I don't ask doesn't mean I don't care. Once, who cried for whom. You are the sand blown into my eyes, which blurs my eyes and can't see the sky clearly. This is a busy ending, not the whole city or this country, but everything to me. What do you want, to be together all your life, or to live well; All I want is a simple and stable life. Love to death, running water under the bridge The best happiness is the care you give.
What is the relationship between a and the eigenvalue of A*? When a is invertible, if λ is the eigenvalue of a and α is the eigenvector of a belonging to the eigenvalue λ,
Then |A|/λ is the eigenvalue of A*, and α is still the eigenvector of A* belonging to the eigenvalue |A|/λ.
What is the relationship between the eigenvalue of a matrix and its adjoint matrix? What is the relationship between a matrix and the eigenvector of its adjoint matrix? If 0 is the eigenvalue of matrix A, then 0 is also the eigenvalue of adjoint matrix A*;
If k is a non-zero eigenvalue of matrix A, there is a non-zero vector a: Aa=ka.
Then A*Aa=kA*a
|A|a=kA*a
A*a=(|A|/k)a
|A|/k is the eigenvalue of A*.
What is the relationship between the eigenvector of A and the eigenvector of A+2E? Let λ be the eigenvalue of a,
Then λ+2 is the eigenvalue of A+2E,
If x is the eigenvector of a corresponding to λ,
Then x is also the eigenvector of A+2E corresponding to λ+2.
certificate
Ax=λx
(A+2E)x=Ax+2Ex=λx+2x=(λ+2)x
What is the relationship between a matrix and the eigenvalues of its invertible matrix? What is the relationship between a matrix and the eigenvector of its invertible matrix? The relationship between the eigenvalue of a matrix and the eigenvalue of its inverse matrix is the inverse number.
What is the relationship between the characteristics of sound? A: Sound has three characteristics: tone, timbre and loudness. Tone indicates the level of sound. When we listen to different frequencies, we will feel that the high notes come from higher places and the low notes come from lower places. This is pitch, or tone. Tone refers to the waveform in the basic period; Loudness is the average sound energy passing through a unit area perpendicular to the propagation direction of sound waves in a unit time. The unit is "W/m2".
Tone is related to frequency; Loudness is related to amplitude.
From the perspective of auditory psychology, the three characteristics of sound are loudness, pitch and timbre.
In terms of physical characteristics, sound is a kind of vibration, or an alternate change in the displacement or speed of particles such as air molecules. Or it is a fluctuation phenomenon that the air density changes its density repeatedly and gradually expands to the surrounding space. If the vibration state is expressed by basic measures, there are three kinds: vibration intensity, vibration frequency and vibration waveform. The size of sound is slightly equal to the intensity of vibration, the pitch is slightly equal to the frequency, and the timbre is very close to the waveform.
I. Tone (pitch)
There are many kinds of sounds, each with its own characteristics. One of the characteristics of sound is called tone.
For example, the voice of girls is higher than that of boys, and the voice of the right key is higher than that of the left key. This is caused by the different times (frequencies) of sound wave vibration per unit time. Generally speaking, we also have an auditory experience, that is, the vibration tone of larger objects is lower. However, smaller objects vibrate at a higher pitch, for example, drum vibration sounds have a lower pitch. The aftershocks are also longer, the pitch of the snare drum is higher and the aftershocks are shorter.
What is tone?
The best way to explain tones is to use scales.
Relative frequency of scales *
Music notation and the name.
C
D
E
F
G
A
B
C 1
1
2
three
four
five
six
seven
1
do
about
The third note of the major scale.
The fourth note of the major scale
sol
The sixth note of a diatonic scale.
The seventh note of the major scale
do 1
Chinese phonetic names
Dou (surname)
Laai music
The third note of the major scale.
The fourth note of the major scale
short for Suzhou/short for Jiangsu Province/short of the Soviet Union/a surname
The sixth note of a diatonic scale.
The seventh note of the major scale
dou 1
frequency
2569
288
320
34 1
384
462
480
5 12
relative frequency
Minimum integer
24
27
30
32
36
40
45
48
mark
1
9/8
5/4
4/3
3/2
5/3
15/8
2
space
9/8 10/9 16/ 15 9/8 10/9 9/8 16/ 15
A scale is a series of pure tones, in which the interval between the first pure tone and the last pure tone is equal to 1 octave.
You may know what a scale is. Sing by yourself according to the scale. Sing, open your mouth and sing! Do，re，mi，fa，sol，la，ti，do！ Note that the pitch is getting higher and higher.
A scale consists of sounds with different tones. Every sound has its own tone. So the tone indicates the level of the sound. Tone does not indicate the size of the sound.
How are tones formed?
Tone depends on the vibration frequency of the sound source-the number of times an object completes periodic vibration in one second. Unit: Hertz. One hertz is one second of vibration.
The faster the object vibrates or the higher the vibration frequency, the higher the tone. The slower the object vibrates or the lower the vibration frequency, the lower the tone. The sound of playing the flute belongs to high notes. Tuba is played in a low voice. Because the flute vibrates faster than the tuba.
Words are the most important part of a language. But tone is also important. Your tone is constantly changing when you speak. The change of tone increases the meaning of words. They help you express what you want to say.
Tone sandhi is also the most important part of music. Can you imagine music with only one tone? Can you imagine a guitar or piano with only one sound? How monotonous the world would be if there were no changes in hue!
How does the tone change?
In order to change the pitch, we must change the speed of vibration. The following factors change the vibration speed.
1. Compact
▲ The tighter the object, the faster the vibration. The higher its pitch becomes.
▲ The more relaxed the object, the slower the vibration will be. The lower its pitch becomes.
2. Length
▲ The shorter the object, the faster the vibration. The higher its pitch becomes.
▲ The longer the object, the faster the vibration. The higher its pitch becomes.
3. Thickness or thickness
▲ The thinner the object, the faster the vibration. The higher its pitch becomes.
▲ The thicker the object, the faster the vibration. The higher its pitch becomes.
4. Tone change
Language is produced in the throat. Laryngeal vocal cords. Vocal cords can change shape and change.
When you don't talk, your vocal cords don't close. They didn't shake.
When you speak, the vocal cords are closed, and air from the lungs passes through the vocal cords, making them vibrate. This vibration produces sound.
When you speak, the tightness of the vocal cords will also change. The two vocal cords will also be slightly closer or farther away. These changes cause changes in tone.
The frequency of some sounds (sound waves)
Sound (sound wave)
Frequency (Hz)
Human lung function
0.03~0.25
Human heart sound wave
1~2
Low frequencies that mice can hear.
16 or less
Mosquito calls
Thousands.
The frequency of bees' wings when flying
220~440
The highest frequency that dogs can hear.
38000
The speed at which most people can hear sound.
16~20000
The speed at which ordinary people make sounds.
64~ 1300
The speed of speech that is very sensitive to human beings.
1000~3000
Whistle and sound
dozens of
The lowest note on the piano.
27.5
The highest note on the piano
4096
C tone (dou) frequency
256
Drum or cello
100~200
Flute or whistle
5000~8000
infrasound
16 or less
supersonic
More than 20,000
High-frequency ultrasound obtained by modern technology
109
Two. roll
Volume: Sound has energy.
Decibel: A unit for measuring sound.
The volume range is very wide. Some sounds, such as people whispering or birds chirping, are very low in volume. They are soft sounds. Other sounds, such as the rumble of jets or the explosion of explosives, are loud. In fact, some of them are so loud that we have to cover our ears.
During the day, you are controlling all kinds of changes in trading volume. You adjust the volume of the radio or TV. You change the volume of your speech. Sometimes, people say to you, "Speak louder, I can't hear you." Sometimes, people will ask you to "speak softly". Isn't this often heard? There is also a common saying: "Please turn down your radio, it will burst my eardrum!" " "
What caused the volume?
As we all know, pitch or tone depends on frequency. Frequency is the number of times an object vibrates in one second.
The volume varies depending on the energy of the sound. The energy of sound depends on the amplitude of sound waves in the medium. As shown in the following figure 1:
The greater the amplitude of sound, the greater the energy and the greater the volume. Strictly speaking, talking about volume involves two related but different concepts-sound intensity and loudness.
Physical definition: the average sound energy intensity per unit area perpendicular to the sound wave propagation direction in unit time. The unit is "W/m2".
Sound waves that can cause human hearing require not only a frequency of 20 Hz to 20HZ~20000HZ, but also a sound intensity of10-12w/m2 ~1w/m2. Visible sound intensity range is very large. In acoustics, "sound intensity level" is often used to describe the intensity of sound waves at various points in the medium. Sound intensity I0= 10- 12W/ m2 is defined as the standard for measuring sound intensity. If the sound intensity of the sound wave is I, the logarithm of the ratio I/I0 is called the sound intensity level L of the sound intensity I, that is, L=lg(I/I0), and the unit of L is "bell". Because this unit is too large, in fact, its110, that is, "decibel", is often used as the unit. So "sound intensity level" L= 10lg(I/I0) decibels. Using sound intensity level to express sound intensity is not only convenient for measurement, but also because people have different sensitivities to sound waves of different frequencies, so sound waves with the same sound intensity and different frequencies sound different in loudness. That is, objectively, the volume is the same, but subjectively, the human ear feels that the volume is different. But the loudness of sound perceived by human ears is directly proportional to the sound intensity level.
That is, "decibel" is used as the unit of loudness. The higher the decibel number, the louder the sound.
The decibel value is counted from zero. Zero decibel sound is the starting point of human hearing. 140 decibel sound can make us lose our ears. For example, can you turn up the radio or stereo system very loudly? Listening to loud music for a long time may impair your hearing, and it is permanent.
Sound intensity level, sound intensity and perceived loudness of some sounds
sound source
Sound intensity level (decibel)
Sound intensity (w/m2)
volume
Auditory threshold (olfactory threshold)
10— 12
The smallest sound a person can hear.
soundproof room
whisper
Blade wear
0~20
10— 12~ 10— 10
Extremely light
Dialogue (light)
Residential (static)
Office (static)
20~40
10— 10~ 10—8
light
Residential (busy)
Office (average)
40~60
10—8~ 10—6
normality
factory
busy street
60~80
10—6~ 10—4
loudly
police whistle
lorry
80~ 100
10—4~ 10—2
Very loud
riveting hammer
thunder
big shot
100~ 120
10—2~ 100
shock wave
threshold of pain
120
100
My ears began to feel pain.
Third, the sound (tone quality, timbre)
Pitch: the lowest tone that an object can emit when it vibrates.
A tone (also called overtone) that is higher than the pitch produced by the same object.
People's ears are sensitive. When they hear a sound, they can immediately tell what it is. It's human voices, musical instruments, cars or dogs barking. The human ear can also tell whether the voice is a boy or a girl, whether it is Zhang San or Li Si, whether it is knocking on copper or iron. No matter the sound of knocking on wood or stone, the human ear can recognize almost unlimited sounds, and the auditory impression corresponding to this recognition is timbre. Timbre, also known as timbre, is the characteristic of sound perceived by hearing. Pure tones have no timbre problems, while polyphones have timbre differences. Timbre is mainly determined by the frequency spectrum of sound, that is, the composition of pitch and harmonics, and is also related to the waveform, sound pressure and time characteristics of sound. If the phonograph record rotates in the opposite direction, the frequency spectrum of the sound remains unchanged, but the timbre changes significantly. This shows that timbre is largely related to the amplitude fluctuation characteristics of overtones at the beginning and end. ?
Timbre is of great significance to the development of electronic musical instruments. At present, electro-acoustic simulation is used to make electronic musical instruments, which is based on the frequency spectrum, pitch and relative intensity of harmonics of various musical instruments.
Play a song on the piano and the same song on the guitar, trumpet or flute. Their tones are the same, but the "sound" of each instrument is different. You can tell them apart without any difficulty. Each instrument has its own unique sound or special sound quality.
Sound quality makes it easy for us to distinguish various sounds. Take talking as an example. Suppose a friend calls you at the corner. Who's calling you? You can distinguish the sound from the sound quality. How can sound have a special quality?
The tuning fork vibrates at only one frequency. But most pronunciations are not like this. Most pronunciations vibrate at different frequencies at the same time. Each vibration frequency produces its own tone.
Take vibrating string as an example. The vibration of the whole string produces a certain tone. At the same time, each part or segment of this string vibrates faster, thus producing a higher tone.
▲ The tone produced by the whole string is called pitch. This is the lowest sound that this string can make.
▲ The higher pitch produced by the segmentation of strings is called doubling. The pitch of an octave depends on how many segments the string is divided into. The more vibration segments, the higher the pitch.
Pitch and octave mix together to determine a person's sound quality. Many sounds have more than one octave.
Several pitches, octaves and volumes are combined in various ways to produce different quality sounds. The spectrogram of different sounds is different.
We know that there is no pure tone sound wave of sine wave in nature, and the sounds made by objects in nature are all complex waveforms. Each has its own, this complex waveform in addition to the basic frequency waveform. There will also be a series of resonance frequencies, which we call "harmonics". It has a certain "two-tone" relationship with the tonic, for example, the fundamental frequency of object vibration is 240Hz. Such as 480 Hz (second harmonic) and 720 Hz (third harmonic). It also happens, and the octave component of each object is different. This different object produces different octave components, which are timbre.
The pitch audio range of the instrument is about 20 Hz ~ 4000Hz, so the audio can only reach 4000Hz. Then why does the frequency response of the sound system need to reach 20KHz? That's because all the above frequencies are the pitch of musical instruments, and the sound of musical instruments has a series of overtones besides the pitch. For example, the highest pitch of a piano is 4 186 khz, but overtones can be as high as 16KHz. Moreover, the composition and proportion of overtones of each instrument are different. Therefore, the sound of each instrument is different, which is also the place where the timbre of the instrument is fantastic and unpredictable.
Violin and trumpet sound the same, but the timbre of these two instruments is different. This proves that the overtone composition of violin and trumpet is different.
How to distinguish timbre from timbre?
Literally, the so-called "sound" refers to the sound waves transmitted through the air by objects due to vibration, which can be felt by people's ears. And "timbre" is because of the homophonic sound.
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What is the relationship between parental rearing patterns and children's personality characteristics? At the beginning of life, a kind-hearted child has just been born. Except for some natural characteristics, everything acquired is cultivated by parents' words and deeds and family environment.