Professional analysis of acoustic frequency range and frequency response
In practice, the frequency range and frequency response of the sound have always been a concern, but because of the professional segmentation knowledge, many people have a relatively one-sided understanding of the frequency range and frequency response. What is the difference between the frequency range and the frequency response? Is the higher the frequency, the better the sound effect? How high is the sound frequency? For such problems,
Xiaobian made the following compilation:
First, the definition of frequency range and frequency response
The frequency range refers to the range between the lowest effective playback frequency and the highest effective playback frequency that the sound system can reproduce; the frequency response refers to the sound pressure generated by the speaker when the audio signal output with a constant voltage is connected to the system. The phenomenon of increase or decrease and phase change with frequency changes. The relationship between the sound pressure and the phase and the frequency (change amount) is called the frequency response in units of decibels (Db).
Second, the sound system frequency discrimination
The frequency characteristics of the sound system are often described by the ordinate of the decibel scale representing the power and the frequency response curve of the frequency represented by the abscissa of the logarithmic scale. When the sound power is 3 dB lower than the normal power, this power point is called the high frequency cutoff point and the low frequency cutoff point of the frequency response. The frequency between the high-frequency cut-off point and the low-frequency cut-off point is the frequency response of the device; the curves of sound pressure and phase lag with frequency are called “amplitude-frequency characteristics” and “phase-frequency characteristics”, respectively. characteristic". This is an important indicator to check the performance of the speaker. It has a direct relationship with the performance and price of the speaker. The smaller the decibel value, the flatter the frequency response curve, the smaller the distortion and the higher the performance. Such as: a speaker frequency response is 60Hz ~ 18kHz +/- 3dB. These two concepts are sometimes indistinguishable and are called frequency response.
Third, how high is the audio frequency?
In theory, a frequency response of 20 to 20,000 Hz is sufficient. Sounds below 20 Hz, although not heard, but other human sensory organs can be perceived, that is, the so-called bass strength can be felt, so in order to perfectly play various instruments and language signals, the amplifier must achieve high fidelity goals. The harmonics of the tones are reproduced. Therefore, the frequency band of the amplifier should be extended, the lower limit should be extended below 20 Hz, and the upper limit should be increased above 20,000 Hz. The representation of the frequency response of the signal source (receiver, recording deck, and CD player) is different. For example, the frequency response of the FM stereo broadcast specified by the European Broadcasting Union is 10/-2dB when the temperature is 40 to 15000 Hz. The minimum frequency response specified by the International Electrotechnical Commission for the recording studio is 10/-2.5/10/-4 when 40 to 12500 Hz. 5dB (common band), the actual achievable indicators are significantly higher than this value. The upper limit of the frequency response of the CD player is 20000 Hz, and the low frequency end can be made very low, only a few Hertz, which is one of the reasons for the good sound quality of the CD player.
Fourth, the wider the frequency range, the better the sound effect?
The harmonic components that make up the sound are very complicated. The wider the frequency range, the better the sound is, but this is basically correct for medium and low-end multimedia speakers. In the labeled frequency response, we usually see the terms "system frequency response" and "amplifier frequency response". We must know that the "system frequency response" is always smaller than the range of "amplifier frequency response", so only the label is marked. "Amplifier frequency response" does not make any sense, it is only used to deceive some unsuspecting consumers. Nowadays, the speaker manufacturers generally have a wide range of system frequency response, and there are not many high-frequency parts, but the annotation on the low end is extremely unreal. The foreign famous HiFi (high-fidelity) speakers are also marked with 4, 50Hz or so. And the domestic two or three hundred wooden ordinary speakers actually dare to mark this data, it really makes people laugh big teeth! Therefore, we must tell everyone that the low-frequency sound must be heard, and don't trust the value on the flyer. The music in the multimedia speaker is mainly based on the music, songs, sound effects of the game, background music and the vocal and environmental sound effects in the film. These sounds are mainly medium and high sounds, so when selecting multimedia speakers It should be more focused on its ability to express sound in the mid-to-high range, rather than the low frequency band. If you really want the cinema effect, then a powerful subwoofer can definitely meet your needs.