How to "listen" to the sound quality of the speaker?
In the face of a speaker, how to evaluate its sound quality? This is difficult for many audio and video enthusiasts to grasp. Sometimes, we will encounter a situation where the same speaker, different people will give different sound quality evaluation. Then, is there a set of subjective evaluation criteria in the industry, and there is no relevant standard at present? But we can conduct subjective evaluation of sound quality by using rigorous and scientific methods as much as possible. Below, the author will introduce some relevant knowledge of subjective evaluation of sound quality.
For audio equipment or cinema systems, their sound cannot be measured completely using parametric indicators. The subjective evaluation of audio equipment is to evaluate the characteristics of the equipment by listening to the environment and the conditions under which the program can be controlled. Moreover, subjective evaluation of a single piece of equipment is often difficult, so it is usually compared with standard equipment or between multiple pieces of equipment to obtain loudness, frequency range, tonal balance, spatial distribution, quality and unevenness. The combined effect of factors such as factors and evaluation results.
First, the subjective evaluation of sound quality should meet the conditions
The quality of sound quality depends on a variety of 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 degree, etc., sound field characteristics (such as direct sound, pre-reflected sound, reverberant sound, cross-correlation coefficient, 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 material
The use of different program sources in evaluating sound quality will have a great impact on the evaluation results. Therefore, the source of sound quality evaluation should not only be comprehensive, but also include different genres and styles of music and voice, and should have strict recording and production requirements. Sufficient frequency band and amplitude.
(2) Adopting current high-performance system equipment
When listening to an audio equipment, it must be composed of the product and other audio equipment to form a sound playback or pick-up system. Due to the rapid development of the audio industry, in addition to the obvious differences in objective indicators, different equipments and equipment also have their own inherent "tones", so there is no such thing as "standard sounds". This requires that the current best equipment be selected as much as possible in the subjective listening evaluation to reduce its introduction of additional influence factors for subjective evaluation. Nowadays, there are many top-level "reference grade" products introduced by many manufacturers in the world. Although it can not 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 influence of the listening environment on the sound quality is unquestionable. Because the structure, shape, volume and internal surface sound absorption processing methods of different listening rooms are different, the acoustic parameters of the room are different. In this way, listening to the same audio product in different rooms will lead to different conclusions. Therefore, the listening room used for listening evaluation should standardize 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, light, and prevent these factors from affecting the mood of the auditor.
(4) Requirements for sound quality assessment personnel
Because the sound quality evaluation has a strong personal subjective color, the individual differences in the professional, physiological, emotional and cultural accomplishments of the listener directly affect the evaluation results of the sound quality. Therefore, in the subjective evaluation of 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 of the human ear itself), but also must have an aesthetic evaluation of sound quality. And the ability to evaluate the sound quality of instruments and other sound sources. At the same time, through the sound quality evaluation can be related to the objective technical indicators of the audio products, when there are small differences in sound quality, what kind of sound is heard by the sound source to distinguish, what attributes are used to judge the difference in sound quality.
In order to minimize the error in sound quality evaluation due to the individual differences of the auditors, an audition team member may include scientific and technical workers engaged in stereo and architectural acoustics, electroacoustics, acoustics, recording, tuning technicians, musicians, and music. Editors and film and music directors, actors.
Second, subjective hearing sound
Usually, according to the three elements of sound, that is, the change, combination of loudness, pitch, and timbre, subjectively evaluate various properties of sound quality, such as low frequency loudness for fullness, high frequency loudness for bright sound; low frequency faint for smooth sound, low frequency faint Clear for the sound. Below we combine the sound source, sound field and signal characteristics to introduce several typical senses of hearing.
(1) Three-dimensional sense
The sound is not only hierarchical, but also has a sense of space. The sound image of various sound sources is accurate and clear, and there is a complete distribution of sound image groups. The sound distortion is small, the dynamic range is large, and the transient response is good, giving an immersive feeling.
(2) Intimacy, natural feeling
The sound changes naturally and smoothly. The loudness, tone, reverberation and balance are just right. It is not exaggerated. The momentum, style and dynamic range are in line with the natural characteristics of the sound source, making people feel intimate, natural and pure and beautiful.
(3) Sense of overallity and community
Refers to the frequency is rich and coordinated, the low frequency is thick and powerful, the high frequency level is clear, the overall momentum is grand and not delicate, the dynamic range is large and smooth, just like the peaks stand and give people the overall beauty.
(4) Sense of integration, balance and harmony
In the condition of wide frequency response, small distortion, high signal-to-noise ratio and large dynamic range, the singing or the various parts of the band are more harmonious and balanced, regardless of volume, pitch uniformity and reverberation. Together.
In addition to the above-mentioned kinds of sense of hearing, when we subjectively evaluate the sound, we will also find that the sound has the following obvious manifestations:
Clear - fuzzy, turbid
It means that the language has good intelligibility and the music is well-defined. When the balance condition and sound transient characteristics are not good, the low sound and the reverb sound are too heavy, which will bring a feeling of "blur" and "turbidity".
Balance - imbalance
It refers to the proportion coordination of the various parts in the program, and the high, medium and low sounds are properly matched. The work itself or the band's compilation often has an imbalance, which can be balanced by tuning and picking up.
Plump - thin, dry
Refers to the sound fusion, especially the middle and low-order overtones are rich, and the high-order overtones are not too prominent. The response is appropriate, the listening is warm, thick and flexible. The signal level is not necessarily full, the transient response is poor, the low-order overtone loss is too much, the mid-bass is weak, the reverberation is insufficient, and the time delay of the previous reflection is improper, which may bring the feeling of thin and dry defects.
Rounded - rough
Beautiful and beautiful, shiny and not noisy. Mainly used to evaluate vocals and instrumental sounds. Excessive treble, obvious distortion, and poor acoustic characteristics of the hall may make the sound rough.
Bright - dark
It means that the high school voice is full, it sounds clear and active. Pre-reflected sound, reverberant sound and direct sound blend well to increase brightness. It is not necessarily effective to focus only on the level of sound pressure that enhances direct sound.
Soft - sharp
The sound is slack, 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 hard.
Maintain the characteristics of the original sound source. When tuning, the unpleasant sound will be suppressed, or the sound source will be modified, and the effort will be made in the direction of the ear, but the original sound will never be deformed, and the original piano will become a black tube. This is not only a must for evaluation language, but also a principle for replaying sound.
Third, the meaning of commonly used listening evaluation terms:
Sound breaks (劈): Severe harmonics and intermodulation distortion, there is a "beep" sound, the flat top has been cut, and the distortion is greater than 10%.
The sound is hard: the bass is lacking, the medium and high frequency is too much, and the high frequency harmonics decay too short and too fast, the low frequency reverberation sound is short, there is obvious intermodulation distortion, and the transient response is not good.
Sound explosion: There are too many high frequency or medium frequency, there are two kinds of distortion.
Sound sanding: The passband distortion is large, with additional high harmonics and transient distortion.
The sound is stunned: the transient is not good, the resonance peak of the speaker is prominent, and the low frequency or medium and low frequency is excessive.
Wide sound: frequency bandwidth, medium and low frequency, good low frequency, moderate reverberation.
The sound is boring: the high frequency or medium and high frequency is too small, or the directivity is too sharp and off the axis.
Fine sound: low density of sound energy, insufficient loudness, slender sound, lack of low frequency, high frequency and high frequency, and insufficient reverberation.
Levels: good transients, flat frequency characteristics, moderate reverberation.
Solid sound: good mid-low frequency, moderate reverberation, and loudness.
The sound is divergent: the intermediate frequency is lacking, the intermediate frequency transient is not good, and the reverberation is too much.
The sound is narrow: the frequency characteristics are narrow, the high and low frequencies are lacking at both ends, the frequency band is not wide, the reverberation is short, and the intermediate frequency is excessively prominent.
Metal sound (lead skin sound): The high-frequency individual points are high and the distortion is serious.
The sound is round: the frequency characteristics are good, the distortion is very small, the reverberation is moderate, and the transient is good.
There is moisture: medium and high frequency and high frequency are good, and the reverberation is enough.
The sound is bright: medium and high frequency and high frequency are sufficient, relatively flat, and the reverberation is moderate.
Sound spike: too much high frequency and medium and high frequency.
High-pitched (floating): lack of intermediate frequency, medium and high frequency and high frequency pointing too sharp.
The sound is dark: lack of high frequency and medium frequency.
Sound dry: lack of reverberation, lack of medium and high frequency.
Balance or concord: good frequency characteristics and low distortion.
Booming: The resonance peak of the speaker is severely prominent and the transient is not good.
Good definition: high frequency and high frequency, low distortion, good transient, moderate reverberation
There is a stereoscopic effect (in mono mode): the frequency response is flat, the reverberation is moderate, and the transient is good.
Transparency: The distortion is small, the transient response is good, the frequency response is wide and uniform, the medium and high frequency and high frequency are available, and the reverb sound is suitable.
The sense of presence or presence: frequency response and transients are good, especially medium and high frequency.
Plump: Frequency bandwidth, good mid-low frequency, moderate reverberation.
Soft (loose): low frequency and medium and low frequency, the sound is slack, the loudness is appropriate, the reverb sound is slightly larger, and the distortion is small.
There is gas (potential), good strength: loudness, good reverberation, low frequency and medium and low frequency.
Conclusion: On the subjective evaluation of the speaker, only in the case of a controlled environment and program source, more comparison and judgment can form an objective and true subjective evaluation.