Faced with a speaker, how to evaluate its sound quality? This is difficult for many video lovers to grasp.
Sometimes, we will encounter a situation, the same speaker, different people will give different sound quality evaluation. So, does the industry have a set of subjective evaluation criteria, and currently there are no relevant standards.
However, we can make subjective evaluations of sound quality through rigorous and scientific methods. Below, I will introduce some knowledge about subjective evaluation of sound quality.
For audio equipment or theater systems, their sound cannot be completely measured using parameter indicators. The subjective evaluation of audio equipment is to evaluate the characteristics of the equipment by listening under the conditions of the environment and the program can be controlled.
Moreover, it is often difficult to perform subjective evaluations on a single piece of equipment, so standard equipment or comparison between multiple equipment is usually used to obtain the loudness, frequency range, tone balance, spatial distribution, quality and unevenness The comprehensive effect perception and evaluation results of other factors.
Conditions for subjective evaluation of sound quality
The evaluation of sound quality depends on various factors, such as sound source characteristics (sound pressure, frequency, spectrum, etc.), signal characteristics of audio equipment (such as distortion, frequency response, dynamic range, signal-to-noise ratio, transient characteristics, stereo sound Separation degree, etc.), sound field characteristics (such as direct sound, early reflection, reverberation, correlation between ears, reference vibration, sound absorption rate, etc.), auditory characteristics (such as loudness curve, audible range, various senses of hearing) )Wait. Therefore, this requires the evaluator to listen to various sound effects in a relatively standard environment.
(1) Selection of signal source and program materials
The use of different program sources when evaluating sound quality will have a great impact on the evaluation results. Therefore, the program sources for sound quality evaluation must not only be comprehensive, including music and voice of different genres and styles, but also have strict recording and production requirements to ensure that there are Sufficient frequency band and amplitude.
(2) Use current high-performance system equipment
When evaluating the sound of a certain audio equipment, it must be composed of the product and other audio equipment to form a sound playback or pickup system. Due to the rapid development of the audio industry, in addition to the obvious differences in objective indicators of different equipment, it also has its own inherent "timbre", so there is currently no so-called "standard sound"
This requires choosing the best equipment at present when evaluating subjective listening, so as to reduce the introduction of additional influencing factors to subjective evaluation. Nowadays, there are many top-level "reference-level" products launched by many manufacturers in the world. Although it cannot be said that these products have reached the ideal level, their excellent performance is enough to be used as standard equipment.
(3) Meeting the acoustic requirements of the listening room
The impact of the listening environment on sound quality is unquestionable. Due to the different structure, shape, volume and internal surface sound absorption treatment methods of different listening rooms, the acoustic parameters of the room are different. In this way, the same audio product will have different conclusions when it is evaluated in different rooms. Therefore, the listening room used for listening evaluation should regulate certain acoustic conditions to reduce the impact of the listening room on the evaluation results. In addition, the listening room should have appropriate temperature, humidity, and light to prevent these factors from affecting the emotions of the audition personnel.
(4) Requirements for sound quality assessors
Because the sound quality evaluation has a strong personal subjective color, the individual differences in the listener's occupation, physiology, mood and cultural accomplishment directly affect the sound quality evaluation results.
Therefore, when subjectively evaluating the sound quality of audio products, the selection of members of the audition group is very important. The members of the audition group not only have high requirements for the sensitivity of the hearing itself (referring to the conditions possessed by the human ear itself), but also must have the aesthetics of evaluating sound quality. And the ability to evaluate the sound quality of musical instruments and other sound sources.
At the same time, the sound quality evaluation can also be related to the objective technical indicators of audio products. When there is a slight difference in sound quality, what kind of sound source to listen to distinguish, and what attributes are used to judge the difference in sound quality.
In order to minimize the error of sound quality evaluation caused by the individual differences of the listeners, a member of the audition group may include scientific and technical workers engaged in stereo and architectural acoustics, electroacoustics, and acoustics, recording and tuning technicians, and musicians and music. Editors and film and music directors and actors.
Generally, the various attributes of sound quality are subjectively evaluated according to the three elements of sound, namely the change and combination of loudness, pitch, timbre, such as low frequency loudness is full sound, high frequency loudness is bright sound; low frequency weak is smooth sound, high frequency weak Clear voice. Below we will introduce several typical listening sensations based on the sound source, sound field and signal characteristics.
(1) Three-dimensional sense and presence
The sound has not only layers and orientations, but also a sense of space. The sound image orientation of various sound sources is accurate and clear, and there is a complete sound image group distribution. The sound distortion is small, the dynamic range is large, and the transient response is good, giving people the feeling of being immersive.
(2) Intimacy and naturalness
The sound changes naturally and smoothly, and the loudness, pitch, reverberation, and balance are appropriate. It is no exaggeration. The momentum, style, and dynamic range conform to the natural characteristics of the sound source, making people feel intimate, natural, and pure and beautiful.
(3) Overall sense and group sense
Refers to the rich and coordinated frequency, the thick and powerful low frequency, the clear high frequency level, the overall momentum is magnificent yet delicate, the dynamic range is large and smooth, as if the peaks stand up and give the overall beauty.
(4) Fusion, balance, harmony
Under the conditions of wide frequency response, low distortion, high signal-to-noise ratio, and large dynamic range, the sound, uniformity, and reverberation of each part of the singing or band are more harmonious and balanced, and the entire sound field is organically fused Together.
In addition to the above-mentioned senses of hearing, when we subjectively evaluate the sound, we will also find that the sound has the following obvious performances:
It means that the language has a good intelligibility and the music has distinct levels. When the balance and the transient characteristics of the sound are not good, the low sound and the reverb sound are too heavy, which will bring the feeling of "fuzziness" and "turbidity".
It refers to the harmonious proportion of the various parts in the program, and the high, medium and low sounds are properly matched. There is often an imbalance in the work itself or in the band's composition, which can be balanced by tuning and picking up.
Refers to the fusion of sound, especially the rich middle and low harmonics, and the high harmonics are not too prominent. The response is appropriate, the sense of hearing is warm, thick and flexible. High signal levels are not necessarily full, poor transient response, low loss of overtones, weak mid-bass, insufficient reverberation, improper time delay of early reflections, etc. may all bring the feeling of thin and shriveled defects
Beautiful and beautiful, shiny and not sharp. Mainly used to evaluate vocals and musical instruments. Excessive treble, obvious distortion, and poor acoustic characteristics of the hall may make the sound rough.
It means that the high school notes are full, sound clear and active. Early reflection sound, reverberation sound and direct sound blend properly, which can increase the brightness. Focusing only on increasing the sound pressure level of the direct sound may not work.
Soft-sharp and hard
The sound is relaxed, not sharp, and has a comfortable and pleasant feeling. If the pickup distance is too close, it will affect the diffusion of the sound and the sound will be sharp and hard.
Maintain the characteristics of the original sound source. During tuning, the unpleasant sound will be suppressed, or the sound source will be modified as desired, and efforts will be made in the direction of sweetness, but the characteristics of the original sound must not be deformed, so that the original piano becomes a clarinet. This is not only necessary for evaluation, but also the principle of reproducing sound.
The meaning of commonly used listening evaluation terms
Sound breaking (splitting): severe harmonics and intermodulation distortion, there is a "pop" sound, the flat top has been cut, and the distortion is greater than 10%.
The sound is hard: the bass is lacking, the middle and high frequencies are too much, and the harmonic decay at the high frequency is too short and too fast, the low frequency reverberation is short, there is obvious intermodulation distortion, and the transient response is not good
The sound explodes: too much high-frequency or mid-frequency, there are two kinds of distortion.
The sound is sandy: the passband is highly distorted, has additional higher harmonics, and is accompanied by transient distortion.
The sound is muddy: the transient is not good, the speaker resonance peak is prominent, and there are too many low or mid-low frequencies.
The sound is generous: the frequency bandwidth, the mid-low frequency, the low frequency are good, and the reverberation is moderate.
The sound is boring: there are too few high-frequency or mid-high frequencies, or the directivity is too sharp to deviate from the axis.
The sound is fine: the sound energy density is small, the loudness is not enough, the sound is thin and weak, the lack of low frequency, partial high frequency and high frequency, and the reverberation sound is insufficient. )
There are layers: good transient, flat frequency characteristics, and moderate reverberation.
The sound is solid: the mid-low frequency is good, the reverb is moderate, and the loudness is sufficient.
Sound divergence: lack of intermediate frequency, poor intermediate frequency transient, excessive reverberation.
The sound is narrow: the frequency characteristics are narrow, the high and low ends are lacking, the frequency band is not wide, the reverberation is short, and the intermediate frequency is too prominent.
Metal sound (lead sound): Individual points in the middle and high frequencies are prominent and highly distorted.
Round sound: good frequency characteristics, minimal distortion, moderate reverberation, and good transient.
Moisture: The mid-high frequency and high frequency are good, and the reverberation is sufficient.
The sound is bright: the mid-high frequency and high frequency are sufficient, relatively flat, and the reverberation is moderate.
Spiked sound: too much high-frequency and mid-high frequency.
Treble (float): Lack of mid-frequency, mid-high frequency and high frequency pointing too sharp.
Dark voice: lack of high frequency and mid-high frequency.
The sound is dry: lack of reverberation, lack of high frequency.
Balance or concord: good frequency characteristics and low distortion.
Roaring: The resonance peak of the loudspeaker is seriously prominent, and the transient is not good.
Good clarity: good mid-high frequency and high frequency, low distortion, good transient, moderate reverberation
Stereoscopic (in mono mode): flat frequency response, moderate reverberation, and good transient.
Transparency: The distortion is very small, the transient response is good, the frequency response is wide and uniform, the middle and high frequencies come out, and the reverberation is suitable.
Feeling of presence or presence: Both frequency response and transient are good, especially in the middle and high frequencies.
Fullness: Frequency bandwidth, good mid-low frequency, moderate reverb.
Soft (loose): Appropriate amount of low and mid-low frequencies, the sound is relaxed, the loudness is appropriate, the reverberation is slightly louder, the distortion is small, and it is bold (potential)
Good intensity: enough loudness, good reverberation, low frequency and mid-low frequency.
The subjective evaluation of the speakers can only form an objective and true subjective evaluation under the circumstances of a controlled environment and program source.