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The basic characteristics of human hearing

The so-called hearing is the subjective response to the sound of people. We know that any complex sound can be described by the three physical quantities of sound: amplitude (sound intensity or sound pressure), frequency and phase. But for the feeling of the human ear, the sound is described in three other terms, that is, loudness, tone and tone, which is what we usually call the "three elements of the sound." In addition, the human ear can distinguish the direction of the sound and reach the human ear and so on. One, loudness

The loudness of the sound is related to the amplitude (sound pressure) of the sound waves. For the same frequency signal, the greater the sound pressure, the greater the loudness. But the human ear on the different frequency of the sound loudness (sensitivity) is not the same, that is, for different frequencies and sound pressure of the same sound, will feel different loudness. Sound in the range of 3 to 4 kHz is easy to feel (high sensitivity), and sound in the lower or higher frequency range is not easily felt. The relationship between sound pressure level and frequency is called equal loudness curve.

1, the human ear for different frequency sound sensitivity is not the same. Specifically, for 3 to 4 kHz voice higher sensitivity, with the frequency to 3 to 4 kHz both ends of the rise and fall, the general trend is reduced sensitivity.

2, the sensitivity of the human ear to different frequency sound is also related to the size of the sound pressure, with the sound pressure reduction, the human ear on the low frequency and high frequency sensitivity should be reduced, especially for low frequency sound is more obvious. This is why when we keep the volume smaller (that is, in the case of low sound pressure level), even if the program has more bass composition, but still beats earphones sounds bass is insufficient, once the volume open (sound pressure level Roughly 80 dB or more), you will feel the bass more rich truth.

As can be seen from the sound curve, if the sound is less than the original sound (recording) sound pressure level playback, by the need to use equalizer to enhance the bass and treble to ensure that the original sound balance. For example, a band playing, if the low-frequency sound and high-frequency sound are about 100 dB recording, because this time the loudness curve is almost straight, so the bass and treble sounds almost loud. If the sound pressure level during playback is low, such as 50 dB, then 50 Hz sound just heard, and 1 kHz sound sounds 50 square, other different frequencies have different loudness Level, so it sounds like low-frequency sound and high-frequency sound are lost, that is, the original sound has changed. At this time to make 50 Hz sound sounds and 1 kHz voice has roughly the same loudness, it must be raised about 20 decibels. Thus we can see that the loudness curve is one of the important basis for using the equalizer.

Second, the tone

The tone is also called the pitch, which is the subjective evaluation scale of the human ear. The level of the tone is mainly determined by the frequency, the higher the frequency, the higher the tone, the lower the frequency, the lower the tone. But the size of the pitch and amplitude also have a certain relationship.

The perception of the tone of the human ear is not a linear relationship, but a logarithmic relationship. In other words, the tone is formed by the relative change in frequency, that is, regardless of the original frequency is the number of the same multiple frequency changes on the human ear always produce the same tone changes. For example, if the frequency is doubled, for example, from 100 Hz to 200 Hz or from 1 kHz to 2 kHz, the tone change is the same in the auditory sense, that is, the so-called "octave" For "octave". It is precisely because the pitch change is proportional to the logarithm (or multiple) of the frequency change. Therefore, in the graph showing the frequency, the frequency coordinates are often logarithmic, and the center of the graphic equalizer is often multiplied by 1/2 Or "1/3".

Each sound of the instrument, in addition to the basic frequency f0, there is an integer multiple of f0 with the harmonic. The tone of each tone is determined by f0, and each harmonic determines the tone of the tone. Sometimes the amplitude of f0 is even smaller than the amplitude of the first few harmonics (eg f1, f2, f3 ...), but f0 determines that the effect of the pitch is not diminished.

The feeling of the human ear is also affected by the amplitude. When the amplitude is large, the eardrums are subject to greater stimulation and deformation, thus affecting the nerve to the tone of the feelings. In general, when the loudness increases, the human ear feels the tone is reduced, the lower the frequency, the more the feeling is reduced.

Three, sound color

In addition to loudness and tone of the human ear has a clear ability to distinguish, but also to accurately determine the sound of beats by dre wireless the sound. The frequency of the different instruments is very different. For example, even if the violin and the piano play the same treble note, people can quickly tell which is the sound of the piano, which is the sound of the violin, and not to confuse each other. This is because they are the same pitch when playing the same note, but their harmonic components (harmonics) are very different in terms of quantity, frequency, and intensity. It is because of the different composition of these harmonics, only to give each instrument unique sound. The tone is mainly related to the frequency structure of the sound. In fact, most of the vibration of the instrument is not a simple harmonic vibration, but by a number of different simple vibration superposition, and these simple harmonic vibration between the vibration frequency to meet the integer multiple relationship. Among them, the lowest frequency is called the fundamental frequency, the fundamental frequency of the harmonic should be called the fundamental wave, the frequency is an integer multiple of the fundamental frequency harmonic called harmonic, in the music vocabulary is called overtone. It is because of the different composition of the harmonic ratio, only to a variety of instruments, voices to the unique sound. If there is no harmonic component, the simple pitch tone signal is no sense of music.

In the sound process, in order to make the sound realistic, you must try to keep the original sound. If some of the frequency components in the sound are enlarged or reduced, they will cause changes in the tone. Sometimes for a particular need, the use of equalizer to make appropriate adjustments to the tone is also possible. It can be seen that the equalizer can make some necessary modification and adjustment of the sound. This is another important basis for the use of equalizers.

Four, Haas effect

Haas found in the experiment that if two different sound sources emit the same sound and arrive at the same intensity at the same time, the subjective feeling is that the sound comes from between two sources; if one of them is slightly delayed (About 5 to 35 milliseconds), it sounds that the two sounds are from the non-delayed sound source, the presence of the delayed sound source has no effect on the orientation, but only increases the loudness; if the delay is between 35 and 50 ms, The presence of a delayed sound source can be identified, but its direction is still in the direction of the sound source that is not delayed; the second sound source is heard like a clear echo when the delay exceeds 50 ms. It can be seen, if in 50 milliseconds (1/10 seconds) beats by dre cheap within the emergence of two identical sounds, generally can not distinguish out, only to be aware of the sound and loudness changes, if the second sound delay 50 ms later Appear, and have enough loudness, we can distinguish them out. This effect is applied to the indoor loudspeaker system, which can ensure the consistency of auditory and auditory audiences in the sound field of distributed loudspeaker systems.

In the hall if the sound of reflection and direct sound of the sound difference is greater than 17 meters, and the room sound effect is not good, it will produce an echo, thus undermining the language of nature and intelligibility. In addition, in the larger hall, in order to ensure the sound field uniformity, often in the backcourt with auxiliary speakers,

At this time for the back seat of the audience, if the mouth of the main speaker to his distance than the backcourt auxiliary speakers to his distance of 12 meters (equivalent to the sound from the mouth of the main speaker than from the backcourt auxiliary speaker sound Delay 35 ms), he will feel the sound from the backcourt, this time, in order to ensure that the audience visual and auditory consistency must be added to the backcourt speakers installed delay. It is also necessary to note that the above is always assumed that the sound volume of the two sound sources is the same, in fact, if the delay does not exceed 20 to 30 milliseconds, you can attenuate the volume of the leading channel (or increase the volume of the lag channel) , To change the position of the image.

Five, sense of direction

Listening, people can use the ears to determine the direction of sound, to determine the location of the sound source. This is because we have two ears (the so-called "binaural effect"), ears spacing is about 20 cm, from the same sound source to reach the ears when the time, strength and phase, etc. are different, From this difference, we have completed the "sound image" of the positioning.

Human ear length on both sides of the head, for the horizontal direction of the azimuth resolution than the vertical direction of the resolution is much stronger, usually can distinguish the horizontal direction of 5 锟斤拷 ~ 15 锟斤拷 changes, but in the vertical direction, Sometimes more than 60 锟斤拷 to distinguish it.

The sense of the sense of a sense of the sense of hearing, so that we in a noisy environment may be "preoccupied" to hear from a certain direction of a more special voice, if we put an ear plug, with a single ear to listen to the above The sense of direction will disappear, then listen to the environment by the interference of serious, vague voice. The use of the sense of the direction of the sense of hearing this feature, we require the layout of the speaker in the hall, as much as possible to ensure that "as", "listen" in the same direction, that is to let the ears hear the sound source and eyes to see the sound Source from the same direction. This requires us to use the "centralized" sound reinforcement system - the speakers on both sides of the stage, and the speaker in the horizontal direction as close as possible to the sound source, as it is in the vertical position of the level, often less affected.

Here is the mention of what is the stereo? The so-called stereo is that people can hear the sound source in the spatial distribution of a sound way. Stereo is based on the human ear effect developed, and now the most simple and practical stereo is the two-channel stereo, it uses two speakers to reproduce the sound, people can pass the sound of two speakers to reach the relative strength of the human ear, the time difference And the phase difference to hear the distribution of the sound source between the two speakers. So we only need to adjust the sound of the two speakers in the relative intensity, delay time and phase can change the positioning of the image. If you want to reproduce the sound source in the entire plane on the distribution must use surround sound, to achieve surround sound usually need four channels, Dolby stereo is one of the best representatives of this stereo. Now we use the surround sound processor can be ordinary two-channel stereo field into four-channel surround sound, in fact, this is just a simulation, is a pseudo-surround sound, it can not really reproduce the sound source Real location. It must be stressed that: do not think that simply install a few speakers is stereo, although this may make the sound sounds more full and round, in fact, only a similar reverb effect.

In addition, the human ear can be based on the difference in sound quality, to distinguish the distance from the sound source, that is, the human ear is not only "directional" ability and "positioning" ability.

Six, Doppler effect

When the sound source and the listener relative movement with each other, will feel a certain frequency to determine the tone of the tone changes. For example, when the train came over

Of the whistle is slightly higher frequency tone, and vice versa when the train to hear the frequency slightly lower tone. This phenomenon is called the Doppler effect.

When the sound source moves at a certain speed and the listener is stationary, the sound intensity (sound pressure) also has a similar change, and the sound source closer to the sound source is at the same distance than it does not move. The intensity of the removed sound source is smaller.

Seven, the impact of noise on clarity

Kara OK hall encountered noise mainly electrical noise and environmental noise two types. In recent years, with the rapid development of electronic technology, the emergence of new digital recording methods and a large number of excellent performance of imported equipment, but also the use of electronic noise, noise and noise, The thermal noise in the electrical noise and the background noise of the recording medium have become less noticeable, so the electrical noise is mainly due to the noise and induced noise caused by the shielding or poor grounding in the wiring, which can be improved by improving the wiring process or using noise Door to suppress. So here we focus on the impact of environmental noise on clarity.

The presence of noise causes a decrease in the hearing of the target sound, that is, the so-called "masking phenomenon", which depends not only on the size of the sound pressure of the noise but also on its frequency components and spectral distribution. Simply put, the main features are the following:

1, low-frequency sound, especially in the loudness is quite large, the high frequency sound will produce a more obvious masking effect.

2, high frequency sound on the low frequency sound only produce a small masking effect.

3, the closer the masking sound is to the frequency of the masked sound, the greater the masking effect, and when their frequencies are the same, the effect of one sound on the other is maximized.

It can be seen that low frequency noise (such as fan noise) and vocals are the main sources of noise that constitute interference. In general, the karaoke hall requires an ambient noise level of less than 30 to 35 decibels, which is an important requirement to ensure clarity.