Sound pressure level standard
The sound pressure level standard of THX certified home theater is: all seats can reach 105dB limit undistorted sound pressure level at 1kHz, and the sound pressure difference between left and right channels is not more than ±3dB between each seat.
Note: Decibel dB is a measure of sound pressure level, + 6dB volume doubled, - 6dB volume doubled. 3dB is the difference in sound pressure that the human ear can clearly feel, so the sound system often uses ±3dB as the allowable distortion range.
What is the sound of â—‹105dB?
According to Wikipedia, chat (distance 1 m) is 40~60dB, bus (distance 10m) is 60~80dB, busy road traffic (distance 10m) is 80~90dB, road construction is used to drill the ground, å“’å“’The slamming machine (distance 1 m) is 100 dB, the aircraft engine (distance 100 m) is 110~140 dB, and the Vuvuzela horn (1 m distance) that the fans are blowing is 120 dB (above) All Vuvuzela Horns at World Cup Made in China), the M1 rifle launch (distance 1 meter) is 168dB. 120dB may cause hearing damage and the ear pain valve is at 130dB.
According to China's industry standards, the maximum sound pressure level of various venue indoor sound reinforcement systems is: gymnasium level 105dB, level two 98dB; music, opera performance level 109dB, level two 105dB; modern music, rock music level 109dB, two Level 106dB; the first stage of the performance is 106dB, the second level is 103dB.
The 105dB is 15dB less than the 120dB of hearing impairment (2.5x volume), and 105dB is only the maximum peak, not the continuous value. Only a long-term exposure to noise levels above 85dB (another saying is 90dB) will cause hearing damage, which is the biggest risk of listening to music with headphones.
The core of the THX standard should be "limit without distortion." For example, weightlifting, "limit without distortion" is the maximum weight that can be lifted without the technical movement being deformed. Zhang San's limit is 100 kilograms (105dB), Li Si is 50 kilograms (99dB), all are 50 kilograms (99dB), who has a higher success rate? Of course, Zhang San, and easy to move, the action must be better than Li Four more standard and better looking.
Know the article "HIFI tenderness, AV stimulation?" said: If the ability of the sound is not enough, the dynamics are not enough, it is difficult to faithfully restore the difference between gunshots and cannons. 3dB is the difference in sound pressure that can be distinguished by the human ear. In the movie sound production, if the gun sound is set to 99dB, the heavy machine gun is 96dB, and the pistol is 93dB. If the maximum sound pressure level of the system is only 93dB, then the gun, heavy machine gun and pistol are all the same volume, but the sounds of cymbals, cymbals and cymbals are different. It’s the same as being shot in a gun and being hit by a pistol. It’s impossible to restore the original intention of sound production. How can you appreciate the feelings the director wants to express?
After upgrading to version 10.0, it is finally possible to open the front panel of Onkyo AV to a 0X THX standard volume without feeling noisy. Download the UE SPL sound pressure meter (pictured right) with the iPhone, measure the sound pressure level of the emperor, play the most intense segment of the final battle of Transformers 3, and occasionally reach the maximum peak of 99dB.
Play music programs, such as "Life Miracle Toscani Concert", "Adele Royal Albert Hall Concert" (left picture, taken from Douban movie), "winged high flying · Italian vocal juvenile IL VOLO 2012 Detroit Opera Concert (middle), although the maximum peak is 99dB, but the climax continues to stay at around 98dB.
I did not expect that the sound pressure level of music is greater than the war in the movie. This may also explain why the industry-level standard “music, opera, rock†is 109dB, which is larger than the stadium's 105dB. In fact, the M1 rifle is already 168dB, so the war can only be fake and virtual, and the music is real.
What is the concept of 99dB peak? In the living room, Optimus Prime has been playing dark, the sun and the moon are dark, and the concert is also very lively. Why is the peak not reaching 105dB? I am thinking about this question, and I think of two things for the time being:
105dB is a very large volume. In order to protect the audience's hearing, the upper sound pressure level is set to be 99dB twice as large in film and music production. 105dB is only the limit standard. As long as 105dB is not distorted, then 99dB, which is twice as small, can be easily handled, and it is easy to handle, not noisy, nice, and resistant. Loud and not noisy is a measure of whether the sound is HIFI. Why is it noisy? Because it is beyond the capabilities of the system, the movement is distorted and distorted.
The iPhone's microphone is not as accurate as a professional sound pressure meter and may be biased. The iPhone 4 results in 6dB less than the iPhone 5, which used to be 93dB at home and in the cinema. Use the iPhone 5 to go to another movie center to measure the sound pressure level of the Hobbit, and hit it with a peak of only 99dB. In fact, 99dB is very loud at home or in the cinema. If you double it, I might have to lick my ears like sitting in the front row. The standard is 105dB, the production is 99dB, is it true?
Although the iPhone's microphone is not professional enough, it is always more objective than the human ear. With it, HIFI will no longer be like the past, there is no standard, no comparability, each flower is in the eyes, can not be divided into high and low. Newly introduced enthusiasts, go to the old home, pick up this new weapon, ask him to adjust the volume to 99dB, if you don't feel the noise, it is so good, then it is the true ginger, you can ask for advice.
Note: The sound pressure meter has two measurement curves, A and C. A is the default curve and C can measure more low frequencies. So set the Frequency Sizing of the UE SPL to C.
THX Reference Level
The literal translation is “THX reference levelâ€, which is “THX standard volume†or “THX standard sound pressure levelâ€. It is a technical article of THX official website. The full text is translated as follows:
THX-certified audio products are designed to give you the perfect experience for your movie. Adjusting the volume of the THX-certified AV preamp to “0†is the standard volume of THX, which is the same volume used by filmmakers and sound artists in post-production studios.
When you watch a movie at the "0" volume with a THX-certified AV preamp, you can experience all the sound elements exactly as you would with the producer, including the exact same fidelity, detail and clarity.
â—‹ What is the standard volume?
It's not easy to make AV preamps and speakers that can reach the THX standard volume. It takes a huge amount of power to drive the sound system and effortlessly achieves no clipping or distortion (ie no distortion) sound effects. To ensure that audio products can achieve this peak performance, THX has developed a number of standards including THX Ultra2, THX Select2 and THX I/S Plus certification.
☆ Professional studio clarity: The THX-certified AV preamp can replay the reference level of a professional studio, ie 85dB sound pressure level and 20dB margin. - This is the source of the 105dB standard, not to achieve 105dB, but to reserve 20dB of margin, to ensure that no distortion of sound is achieved without distortion, no distortion is high fidelity, that is, HIFI. Who dares to say that AV and HIFI can't have both?
☆ Meet the standard volume of the room: Different certification standards are available for different room sizes, including THX Ultra2, THX Select2 and THX I/S Plus.
☆ Distortion-free playback: THX-certified AV preamps and speakers can reproduce standard sound pressure levels in a room of a certain size with minimal distortion.
â—‹Appreciate below the standard volume
Of course, the standard volume is loud and may cause dissatisfaction from neighbors. However, when you turn down the volume, the bass, surround and other sound effects will be lost, or it will feel different from the original film. To this end, THX has developed a THX Loudness Plus technology that allows you to experience rich audio details while watching movies and games without driving your neighbors crazy.
Recently, I made a RoomPerfect in Mr. L's theater. The sound pressure level of the Maijingtu MX150 playback test tone is adjustable, set to 80dB, and the sound pressure level measured with the iPhone 5 is 80dB, set to 75dB. That is 75dB, indicating that the iPhone 5's UE SPL sound pressure meter is accurate. After translating this article, the confidence that the "standard is 105dB and the production is 99dB" is more sufficient.
According to the "Acoustic Knowledge Hall - Basic Knowledge of Sound Environment Design - Hearing Range" of a website, 100~120dB is the "annoying valve" of the human ear, and 120~140dB is the "pain valve". Watching movies is a pleasure, not annoying. 99dB is the upper limit of the "worry valve", so "the standard is 105dB, the production is 99dB", it should not only be guessed.
More home theater knowledge, all in the CHINAHIFI home theater network, welcome to follow WeChat: cnhifi.
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