Use a frequency analyzer or tape recorder; a digital tape recorder can be connected to a microcomputer;
Loudness: It is people’s subjective feeling of sound intensity and cannot be measured with any instrument. .Generally, the indicator of sound intensity is used. Generally, a sound level meter can be used to measure it.
Bit rate refers to the number of bits transmitted per second. The unit is bps (Bit Per Second). The higher the bit rate, the larger the data transmitted and the better the sound quality.
The recommended bit rate is 192Kbps, the amount of data transferred is moderate, and the sound quality is comparable to CD.
Bit rate
In telecommunications and computing, bit rate (sometimes written bitrate) is the speed at which bits are transmitted through a radio or wire. Its interchangeability is also sometimes exploited at baud rate, which is not generally the same. Note that "speed" in this context does not refer to distance/time but to quantity of "information"/time, and should therefore be distinguished from "propagation speed" (depending on the transmission medium and having the usual physical meaning).
It is usually expressed as bits per second, omitted bit/s, b/s, or informally bps. B should always be lowercase, to avoid confusion in bytes per second (B/s), although this assembly is often ignored.
SI prefix is ??often used:
1000 bit/s = 1 kbit/s (one thousand bits or one thousand bits per second)
1000 kbit /s = 1 Mbit/s (one megabit or one million bits per second)
1000 Mbit/s = 1 Gbit/s (one gigabit or one billion bits per second)
Sound frequency: Use a frequency analyzer or tape recorder. A digital tape recorder can be connected to a microcomputer, or you can use an acoustic spectrum tester. If not, you can also use an acoustic amplifier to amplify the sound to be measured. Just pick up the acoustic electrical signal and test it with an oscilloscope.
Usually we divide the sounds we hear into high, medium and low frequencies according to the frequency range, as follows:
1. Extremely low frequency
From 20Hz The octave -40Hz is what I call extremely low frequency. There are very few musical instruments in this frequency band, probably only double bass, bassoon, horn, organ, piano and other instruments that can reach such a low range. Since this extremely low frequency is not the most beautiful range of the instrument, composers rarely write notes that low. Unless pop music is deliberately arranged with electronic synthesizers, extremely low frequencies are of little use to audio fans. Some people misunderstand one thing, saying that although the fundamental tone of an instrument is not that low, the overtones can be as low as the fundamental tone. In fact, this is incorrect, because the fundamental note of the instrument is the lowest note of the note, and the note will only climb up by two times, three times, four times, five times, etc., and there will be no downward notes. It's like if you tighten a string, the vibration frequency of the whole length of the string is the fundamental tone, and the vibration frequency of one-half, one-third, one-quarter, one-fifth...etc. of the string length is the overtone. The sum of the fundamental tone and overtones is the timbre of the instrument. In other words, even if the fundamental note (pitch) of a violin and a flute is the same, the timbre will be different.
2. Low frequency
The frequency from 40Hz to 80Hz is called low frequency. What instruments are there in this frequency band? Bass drum, double bass, cello, bassoon, bassoon, bass trombone, bass clarinet, tuba, French horn, etc. This frequency band is a major contributor to the rich low-frequency foundation. Usually, most people mistake this frequency band for extremely low frequency, because it sounds really low. If the sense of volume in this frequency band is too little, there will be no rich and surging feeling; and it will cause the mid-to-high frequencies and high frequencies to be prominent, making the sound lose its sense of balance and making it unsustainable to listen to.
3. Mid-low frequency
From 80Hz to 160Hz, I call it mid-low frequency. This frequency band is the most troublesome for Taiwanese audio fans, because it is the culprit of causing ringing in the ears. Why is this frequency band particularly prone to peaks? This is related to the length, width and height dimensions of the small room. In order to remove this annoying peak, most people try their best to absorb this frequency band so that their ears will not be buzzing. Unfortunately, when your ears don't sound booming, the lower bass and upper mid-frequency may have become sunken due to the absorption of mid-low frequencies, making the sound thinner and lacking in richness. What's even more unfortunate is that most people think this situation is correct just because the peak disappears. This is one of the reasons why many people don’t have rich sound in their homes. The instruments in this frequency band include the instruments mentioned in the low frequency band just now. By the way, timpani and bass should also be added.
4. Intermediate frequency
The frequency spanning three octaves (320Hz, 640Hz, 1280Hz) from 160Hz to 1280Hz is called the intermediate frequency. This frequency band contains almost all musical instruments and vocals, so it is the most important frequency band. The biggest misunderstanding readers have about the range of an instrument also occurs here. For example, most of the violin's range is in this frequency band, but most people mistakenly think it is very high. Don't think that the soprano's range is very high. Generally speaking, her highest range is only at the upper limit of the mid-range.
From the above description, you must also understand how important this intermediate frequency is in audio. As long as this frequency is depressed, the sound performance will immediately become thinner. Sometimes, this thinness can easily be interpreted as "fake cohesion." I believe that there are many audio fans who are in the situation of mid-frequency depression without knowing it. The importance of this frequency band can also be analyzed from the crossover point of the two-way speaker. Generally, the crossover points of two-way speakers are mostly around 2500Hz or 3000Hz. That is to say, the tweeter unit is responsible for the frequency above 2500Hz, and the mid-bass unit is responsible for the frequency below 2500Hz. This 2500Hz is about twice that of 1280Hz. In other words, in order to prevent the mid-bass unit from causing too much crossover point distortion at the intermediate frequency limit, designers have raised the crossover point to twice the upper limit of the intermediate frequency, so As a result, the most perfect mid-range frequency can be emitted by the mid-bass unit.
If this statement is correct, what is the use of the tweeter? If you've ever put your ear close to a tweeter, you've heard a "hiss" sound, and that's where most of the overtones are. If there is no hissing sound from the tweeter, and only a mid-bass unit is used to sing music, it will definitely be gloomy. Of course, if it is a three-way speaker design, most of this mid-range frequency will be included in the mid-range driver.
5. Medium and high frequency
From 1280Hz to 2560Hz is called medium and high frequency. What instruments are there in this frequency band? About a quarter of the violin's higher range is here, the upper range of the viola, the upper range of the flute, clarinet, oboe, half of the lower range of the piccolo, cymbals, triangle, etc. Please note that the small speaker is not in this frequency band. In fact, the mid-to-high frequencies are easy to identify, as long as the high range of the string group and the high range of the woodwinds are both mid-to-high frequencies. Many people mistakenly think this frequency band is high frequency, so please pay special attention to it.
6. High frequency
The frequency domain from 2560Hz to 5120Hz is what I call high frequency. For musical instrument performance, there are very few opportunities to get involved in this frequency domain. Because except for the upper range of the violin, the high range of the piano, and the piccolo, most other instruments will not appear in this frequency band. From the crossover point of the speaker, we can find that this frequency range all appears in the tweeter. As I said before, when you put your ear close to the tweeter, what you hear is not the sound of the instrument, but a hiss. From the performance of the tweeter, it can be proved once again that the tweeter rarely emits the fundamental tone of an instrument or human voice. It only emits the high-power overtone of the fundamental tone.
7. Extremely high frequency
The wide frequency band from 5120Hz to 20000Hz is what I call extremely high frequency. You can understand from the fact that very few musical instruments appear in high frequencies that the extremely high frequencies contain only the overtones of musical instruments and human voices. In general, the overtones of musical instruments tend to have smaller energy the higher they are. In other words, the tweeter must be made very sensitive and can clearly reproduce very subtle sounds. From here, something happened that troubled the manufacturing of loudspeaker monomers, that is, how to get the best of both worlds. If a tweeter monomer is desperately designed to push the diaphragm with a very small current in order to clearly reproduce all the subtle overtones, then The high-energy high frequencies and mid-range frequencies that are also responsible for this tweeter are likely to be distorted from time to time, because the energy in these two frequency bands is much greater than the extremely high frequencies. This is one of the reasons why many speakers currently on the market are very clear at extremely high frequencies, but are prone to harshness.
The low frequency you are asking about here should include the mid-low frequency, low frequency, and extremely low frequency mentioned above, which is commonly referred to as bass. It is often seen that the slogan of a home theater says "overweight" Bass and so on, this is it.