How to evaluate the sound quality of a speaker? This is difficult for many AV enthusiasts to grasp.
Sometimes, we will encounter a situation where different people will give different sound quality evaluations for the same speaker. So, is there a set of subjective evaluation standards in the industry? At present, there is no relevant standard.
But we can use as rigorous and scientific methods as possible to carry out the subjective evaluation of sound quality. Below, I will introduce some relevant knowledge of subjective evaluation of sound quality.
For audio equipment or cinema systems, their sound cannot be fully measured using parameter indicators. The subjective evaluation of audio equipment is the evaluation of the characteristics of the equipment by listening methods under the controllable conditions of the environment and the program.
Moreover, it is often difficult to perform subjective evaluation of only a single piece of equipment. Therefore, standard equipment or comparisons between multiple pieces of equipment are usually used to obtain a comparison of loudness, frequency range, tonal balance, spatial distribution, quality and unevenness. The comprehensive effect perception and evaluation results of other factors.
Conditions that should be met in subjective evaluation of sound quality
The evaluation of sound quality depends on many 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 Separation, etc.), sound field characteristics (such as direct sound, early reflection sound, reverberation sound, inter-aural correlation coefficient, reference vibration, sound absorption, etc.), auditory characteristics (such as loudness curve, audible range, various hearing sensations) )Wait. Therefore, this requires the evaluator to listen to various sound effects in a relatively standard environment.
(1) Selection of signal sources 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 different genres and styles of music and voice, but also have strict recording and production requirements to ensure Enough frequency band and amplitude.
(2) Adopt current high-performance system equipment
When evaluating a certain audio equipment, it must be composed of the product and some other audio equipment to form a sound playback or pickup system before proceeding. Due to the rapid development of the audio industry, in addition to the obvious differences in objective indicators between different equipment and equipment, they also have their own inherent "tones", so there is currently no so-called "standard sound".
This requires that the best current equipment should be selected as much as possible in the subjective listening evaluation, so as to reduce the introduction of additional influencing factors to the subjective evaluation. 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) Meet the acoustic requirements of the listening room
The influence of the listening environment on the sound quality is indisputable. Due to the different structure, shape, volume and internal surface sound absorption processing methods of different listening rooms, the acoustic parameters of the room are different. In this way, the evaluation of the same audio product in different rooms will lead to different conclusions. Therefore, certain acoustic conditions should be regulated in the listening room used for listening evaluation to reduce the influence of the listening room on the evaluation results. In addition, the listening room should have suitable temperature, humidity, and light to prevent these factors from affecting the mood of the auditors.
(4) Requirements for sound quality assessors
Because the sound quality evaluation has a strong personal subjective color, the individual differences in the occupation, physiology, emotion and cultural accomplishment of the listener directly affect the sound quality evaluation results.
Therefore, in the subjective evaluation of sound quality of audio products, the selection of the 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 of the human ear itself), but also must have the aesthetics of the evaluation 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 be linked to the objective technical indicators of audio products. When there is a small difference in sound quality in the product, the sound from which sound source is listened to be distinguished, and what attribute is used to judge the difference in sound quality.
In order to minimize the error in the evaluation of sound quality caused by the individual differences of the listeners, an audition group should include scientific and technical workers engaged in stereo and architectural acoustics, electroacoustics, acoustics, recording and tuning technicians, musicians, and music Editor and film and music director, actor.
Generally, various attributes of sound quality are subjectively evaluated according to the three elements of sound, namely loudness, pitch, timbre changes and combinations. For example, low-frequency loudness means full sound, high-frequency loudness means bright sound; low-frequency weak means smooth sound, and weak high-frequency sound Clear the voice. Below we will introduce several typical hearing sensations based on the sound source, sound field and signal characteristics.
(1) Three-dimensional and telepresence
The sound is not only hierarchical, directional, but also spatial. The sound and image azimuth 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 an immersive feeling.
(2) A sense of intimacy and naturalness
The sound changes naturally and smoothly, 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 cordial, natural, and pure and beautiful.
(3) A sense of wholeness and group
Refers to rich and coordinated frequencies, thick and powerful low frequencies, clear high-frequency layers, magnificent and delicate overall momentum, large dynamic range and smoothness, as if a group of peaks stand and give people a sense of overall beauty.
(4) A sense of integration, balance and harmony
Under the conditions of wide frequency response, low distortion, high signal-to-noise ratio, and large dynamic range, each part of singing or band is more harmonious and balanced in terms of volume, tone uniformity, and reverberation, and the entire sound field is organically integrated. Together.
In addition to the above-mentioned sense of hearing, when we subjectively evaluate the sound, we will also find that the sound has the following obvious manifestations:
It means that the language has good intelligibility and the music has a distinct level. When the balance and transient characteristics of the sound are not good, the low sound and the excessive reverberation sound will bring the feeling of "fuzzy" and "turbidity".
It refers to the coordination of the proportions of the various voices in the program, and the appropriate combination of high, medium, and bass. The work itself or the band organization is often unbalanced, which can be achieved through tuning and pickup.
Refers to the fusion of sounds, especially the rich middle and low-order overtones, and the high-order overtones are not overly prominent. The response is appropriate, the listening feels warm, thick, and flexible. High signal level is not necessarily full. Poor transient response, high low-order overtone loss, weak mid-bass, insufficient reverberation, improper time delay of early reflection, etc. may bring the feeling of thin and shriveled defects
Beautiful and beautiful, shiny but not noisy. Mainly used to evaluate human voices and musical instruments. Excessive treble, obvious distortion, and poor hall acoustics may make the sound rough.
Refers to full high and midrange, sounding clear and active. Early reflections, reverberations and direct sounds blend properly to increase brightness. Only focusing on raising the sound pressure level of the direct sound may not be effective.
Soft-sharp and hard
The sound is loose, not sharp, comfortable and pleasant. If the pickup distance is too close, it will affect the spread of the sound, and the sound will be sharp and hard.
Maintain the characteristics of the original sound source. When tuning, the unpleasant sound will be suppressed, or the source of the sound will be modified to make the sound pleasant, but the original sound characteristics must not be deformed and the original piano will become a clarinet. This is not only necessary for evaluation terms, but also the principle of sound reproduction.
The meaning of common listening evaluation terms
The sound is broken (splitting): Severe harmonic and intermodulation distortion, there is a "pop" sound, and the flat top has been cut, and the distortion is greater than 10%.
The sound is hard: lack of bass, too much mid-to-high frequency, and the homophonic decay in high frequency is too short and too fast, low frequency reverberation sound is short, there is obvious intermodulation distortion, and the transient response is not good
The sound exploded: There are two kinds of distortions due to excessive high or medium frequencies.
The sound is sandy: the passband has a large distortion, with additional high-order harmonics, and 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 wide and thick: frequency bandwidth, medium and low frequency, good low frequency, moderate reverberation.
The sound is dull: there are too few high frequencies or medium and high frequencies, or the directivity is too sharp and deviates from the axis.
The sound is fine: the sound energy density is small, the loudness is not enough, the sound is slender and weak, the low frequency is lacking, the middle high frequency and the high frequency are lacking, and the reverberation sound is insufficient. )
There are levels: good transient, flat frequency characteristics, moderate reverberation.
Solid sound: good mid and low frequencies, moderate reverberation, and sufficient loudness.
Sound divergence: lack of intermediate frequency, bad intermediate frequency transient, and excessive reverberation.
Narrow sound: narrow frequency characteristics, lack of treble and bass, not wide frequency band, short reverberation, and excessively prominent intermediate frequency.
Metal sound (lead skin 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 transients.
Moisture: good mid-high frequency and high frequency, enough reverberation.
The sound is bright: medium and high frequencies and high frequencies are sufficient, relatively flat, and moderate reverberation.
Sound spikes: Too much high frequency and mid-to-high frequency.
Treble illusion (gone): lack of mid-frequency, mid-high and high-frequency directions are too sharp.
Dim sound: lack of high frequency and mid-to-high frequency.
Dry sound: lack of reverberation, lack of mid and high frequencies.
Balance or Concord: Good frequency characteristics and low distortion.
Roar: The resonance peak of the speaker is severely prominent, and the transient state is not good.
Good clarity: good mid-to-high frequency and high frequency, low distortion, good transient, moderate reverberation
There is a sense of three-dimensionality (in mono mode): flat frequency response, moderate reverberation, and good transients.
Transparency: The distortion is very small, the transient response is good, the frequency response is wide and uniform, the middle and high frequencies can be produced, and the reverberation sound is suitable.
Sense of presence or presence: Both frequency response and transient state are good, especially the mid and high frequencies are better.
Fullness: wide frequency band, good mid and low frequency, moderate reverberation.
Soft (loose): moderate low frequency and medium low frequency, the sound is relaxed, the loudness is appropriate, the reverberation is slightly louder, the distortion is small, and there is boldness (potential)
Good power: sufficient loudness, good reverberation, good low and mid-low frequencies.
The subjective evaluation of speakers can only form an objective and true subjective evaluation under the circumstances of a controllable environment and program source, and more comparisons and judgments.