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The sound reinforcement system of the school Lecture hall is no longer an orderly combination of single sound equipment, but a sound closed-loop system integrating Architectural acoustics (sound field) and information electronic technology (audio electronic equipment). It also has increasingly high requirements for the environment, requiring the auditorium to have sufficient sound pressure and a uniform sound field distribution. Correspondingly, the sound reinforcement system no longer only provides simple amplification functions, but will present different acoustic effects and usage functions according to different usage requirements. Generally speaking, the sound reinforcement system is mainly composed of microphone, loudspeaker, Mixing console, sound field processor, audio processor, automatic mixing console, digital power amplifier and other equipment.

二、擴(kuò)聲系統(tǒng)設(shè)計(jì)要求

2、 Design requirements for sound reinforcement systems

學(xué)校報(bào)告廳主要承擔(dān)學(xué)術(shù)報(bào)告、會(huì)議等以語(yǔ)言為主的擴(kuò)聲，這就要求音響擴(kuò)聲系統(tǒng)能真實(shí)清晰地還原語(yǔ)言信號(hào)。，系統(tǒng)要保證有良好的語(yǔ)言清晰度和足夠的、均勻的聲壓，語(yǔ)言清晰度頻帶在300～6000Hz。此外，報(bào)告廳也是進(jìn)行歌舞、戲曲、音樂(lè)等文藝表演的場(chǎng)所，需要擴(kuò)聲系統(tǒng)能還原再現(xiàn)各種音源。因此，這就對(duì)信號(hào)的清晰度和豐滿度提出更高的要求。

The school's Lecture hall is mainly responsible for speech based sound reinforcement of academic reports, conferences, etc., which requires that the sound reinforcement system can restore the language signal truly and clearly. Firstly, the system should ensure good language clarity and sufficient and uniform sound pressure, with a language clarity frequency band of 300-6000Hz. In addition, the Lecture hall is also a place for performing songs, dances, operas, music and other artistic performances. The sound reinforcement system is required to restore and reproduce various sound sources. Therefore, this places higher demands on the clarity and richness of the signal.

三、擴(kuò)聲系統(tǒng)的設(shè)計(jì)標(biāo)準(zhǔn)

3、 Design standards for sound reinforcement systems

音量的設(shè)計(jì)標(biāo)準(zhǔn)音量和擴(kuò)聲系統(tǒng)的額定功率相關(guān)，足夠的音量是擴(kuò)聲系統(tǒng)的基礎(chǔ)目標(biāo)要求。根據(jù)行業(yè)標(biāo)準(zhǔn)GB50371—2006《廳堂擴(kuò)聲系統(tǒng)設(shè)計(jì)規(guī)范》對(duì)多功能用途擴(kuò)聲標(biāo)準(zhǔn)要求，以語(yǔ)言類為主的廳堂大聲壓為≥90dB，一舞廳≥103dB，二舞廳≥110dB。音量水平是根據(jù)信噪比和系統(tǒng)運(yùn)行特色來(lái)決定的。

The design standard for volume is related to the rated power of the sound reinforcement system, and sufficient volume is the basic objective requirement of the sound reinforcement system. According to the industry standard GB50371-2006 "Code for Design of Hall Sound Reinforcement Systems", the requirements for multifunctional sound reinforcement standards are that the loud pressure of halls mainly focused on language is ≥ 90dB, the first dance hall is ≥ 103dB, and the second dance hall is ≥ 110dB. The volume level is determined based on the signal-to-noise ratio and system operating characteristics.

音質(zhì)的設(shè)計(jì)標(biāo)準(zhǔn)音質(zhì)主要取決于擴(kuò)聲系統(tǒng)的非線性失真和傳輸頻率特性。國(guó)標(biāo)規(guī)定一廳堂傳輸頻率特性指標(biāo)為以100～6300Hz的平均聲壓為0dB，在此頻帶內(nèi)允許范圍為-4～+5dB，50～100Hz和6300～12500Hz的允許范圍為-8～+4dB。頻率傳輸特性是決定音質(zhì)的關(guān)鍵指標(biāo)，非線性失真也是影響音質(zhì)效果的因素之一。此外，音樂(lè)和語(yǔ)言的清晰度也是衡量音質(zhì)的重要標(biāo)準(zhǔn)。清晰度的衡量方法很多，實(shí)際操作中通常依靠現(xiàn)場(chǎng)的主觀感覺(jué)進(jìn)行評(píng)價(jià)。

The design standards for sound quality mainly depend on the nonlinear distortion and transmission frequency characteristics of the sound reinforcement system. The national standard stipulates that the transmission frequency characteristic index of a hall is 0dB with an average sound pressure of 100-6300Hz. The allowable range within this frequency band is -4~+5dB, and the allowable range for 50-100Hz and 6300-12500Hz is -8~+4dB. The frequency transmission characteristics are a key indicator of sound quality, and nonlinear distortion is also one of the factors affecting the sound quality effect. In addition, the clarity of music and language is also an important criterion for measuring sound quality. There are many methods for measuring clarity, and in practical operations, evaluation usually relies on subjective sensations on site.

聲場(chǎng)的設(shè)計(jì)標(biāo)準(zhǔn)標(biāo)準(zhǔn)要求一廳堂不均勻度為1000Hz時(shí)不大于6dB，4000Hz時(shí)不大于8dB，100Hz處不大于10dB。所以，學(xué)校報(bào)告廳應(yīng)該按照標(biāo)準(zhǔn)來(lái)構(gòu)建聲場(chǎng)，要求有盡可能均勻的聲場(chǎng)。

The design standard for sound field requires that the unevenness of a hall should not exceed 6dB at 1000Hz, 8dB at 4000Hz, and 10dB at 100Hz. Therefore, the school Lecture hall should construct the sound field according to the standard, and the sound field should be as uniform as possible.

四、傳聲器的選擇和應(yīng)用

4、 Selection and application of microphones

傳聲器是整個(gè)系統(tǒng)的“入口”。傳聲器把采集到的聲波信號(hào)轉(zhuǎn)變成微弱的電壓信號(hào)進(jìn)行輸出，這就需要后端的音頻處理設(shè)備把信號(hào)放大提高，因此，如果話筒有雜音輸入，那么后端很難，傳聲器的選擇和使用方法對(duì)擴(kuò)聲質(zhì)量和效果會(huì)產(chǎn)生很大影響。此外，在室內(nèi)存在聲反饋的矛盾，因此，對(duì)傳聲器(話筒)的靈敏度、頻響范圍、指向性都有較高的要求。

The microphone is the 'entrance' of the entire system. The microphone converts the collected sound wave signal into a weak voltage signal for output, which requires the back-end audio processing equipment to amplify and improve the signal. Therefore, if there is noise input in the microphone, it is difficult for the back-end. The selection and use of the microphone will have a significant impact on the quality and effectiveness of sound reinforcement. In addition, there is a contradiction in acoustic feedback indoors, so there are high requirements for the sensitivity, frequency response range, and directionality of microphones (microphones).

靈敏度是指?jìng)髀暺鏖_(kāi)路輸出電壓U和聲壓P的比值。實(shí)際上并不是靈敏度越大越好，靈敏度適中就可，不一定追求高靈敏度。傳聲增益125～6300Hz的平均值不低于-8dB。

Sensitivity refers to the ratio of the open circuit output voltage U of a microphone to the sound pressure P. In fact, the higher the sensitivity, the better. Moderate sensitivity is sufficient, and high sensitivity may not necessarily be pursued. The average sound transmission gain of 125-6300Hz shall not be less than -8dB.

對(duì)室內(nèi)擴(kuò)聲來(lái)說(shuō)，擴(kuò)聲系統(tǒng)所能達(dá)到的聲音大小程度受聲反饋(反饋就是聲音從揚(yáng)聲器經(jīng)功放音箱輸出再傳回?fù)P聲器的過(guò)程。經(jīng)多次反饋達(dá)到一定時(shí)，嘯叫便會(huì)產(chǎn)生)的牽制。因此，在同一擴(kuò)聲系統(tǒng)中，傳聲器靈敏度高了，輸出電壓就會(huì)增大，揚(yáng)聲器發(fā)出的聲音也會(huì)相應(yīng)增大。為了防止反饋嘯叫，不得不把音量調(diào)小，從而達(dá)到良好的擴(kuò)聲效果。

For indoor sound reinforcement, the level of sound that the sound reinforcement system can achieve is constrained by sound feedback (feedback is the process of sound being output from the speaker through the amplifier speaker and then transmitted back to the speaker. When the feedback reaches a certain level multiple times, howling will occur). Therefore, in the same sound reinforcement system, if the sensitivity of the microphone is high, the output voltage will increase, and the sound emitted by the speaker will also increase accordingly. In order to prevent feedback howling, the volume has to be turned down to achieve good sound reinforcement effect.

頻響范圍是指?jìng)髀暺髟谝缓愣晧合?，不同頻率時(shí)測(cè)得的輸出電壓變化值。一般來(lái)說(shuō)，頻響曲線越平越好，對(duì)于會(huì)議話筒，其頻響范圍在250～4000Hz就可以了。設(shè)計(jì)時(shí)應(yīng)將頻譜范圍放在較高的頻段內(nèi)，以提高語(yǔ)言的清晰度。因?yàn)槿说恼Z(yǔ)言頻譜范圍一般在100～4000Hz，所以對(duì)清晰度影響較大的是高頻段。

The frequency response range refers to the variation in output voltage measured by a microphone at different frequencies under a constant sound pressure. Generally speaking, the flatter the frequency response curve, the better. For conference microphones, their frequency response range is between 250 and 4000Hz. When designing, the spectral range should be placed within a higher frequency band to improve language clarity. Because the frequency spectrum of human language generally ranges from 100 to 4000Hz, the high-frequency band has a significant impact on clarity.

傳聲器的指向性是指在某一頻率下，在某一方向的靈敏度與大靈敏度的比值。對(duì)于學(xué)術(shù)報(bào)告、會(huì)議等語(yǔ)言類擴(kuò)聲來(lái)說(shuō)，為有效地預(yù)防、抑制聲反饋引起的聲音嘯叫，要選用有指向性的傳聲器。指向性與接受的聲波信號(hào)頻率有很大關(guān)系：頻率越低時(shí)，指向性越差;頻率越高時(shí)，指向性越強(qiáng)。

The directionality of a microphone refers to the ratio of sensitivity in a certain direction to high sensitivity at a certain frequency. For language reinforcement such as academic reports and conferences, in order to effectively prevent and suppress the sound feedback caused by howling, directional microphones should be used. The directionality is closely related to the frequency of the received acoustic signal: the lower the frequency, the worse the directionality; The higher the frequency, the stronger the directionality.

輸出阻抗是傳聲器輸出端用頻率1kHz聲音信號(hào)測(cè)得的內(nèi)阻的模值，分為高阻抗和低阻抗兩種。我國(guó)使用的是200Ω、600Ω和2000Ω。傳聲器具體有以下應(yīng)用。

The output impedance is the modulus value of the internal resistance measured at the output end of the microphone using a frequency of 1kHz sound signal, which is divided into two types: high impedance and low impedance. The recommended values for use in China are 200 Ω, 600 Ω, and 2000 Ω. The specific applications of microphones are as follows.

1、拾音方式。對(duì)于傳聲器的拾音方式主要分為兩種情況：在進(jìn)行語(yǔ)言擴(kuò)聲時(shí)，話筒的聲軸要正對(duì)演講人;而在進(jìn)行音樂(lè)會(huì)的擴(kuò)聲時(shí)，一般采取立體拾音的方式來(lái)進(jìn)行。

1. Pickup method. There are two main ways to pick up a microphone: when performing language reinforcement, the microphone's sound axis should be facing the speaker; When amplifying a concert, three-dimensional sound pickup is generally used.

2、相對(duì)位置。距離越大越能減少聲反饋，因此，話筒在擺放時(shí)相對(duì)位置要遠(yuǎn)，應(yīng)該盡量降低高度并避免其正對(duì)音箱。

2. Relative position. The larger the distance, the less sound feedback can be reduced. Therefore, when placing the microphone, it should be placed relatively far away, and the height should be reduced as much as possible to avoid facing the speaker directly.

3、傳聲器與發(fā)聲者的距離。一般來(lái)說(shuō)，用作演講的話筒離口型的距離取為10～20cm為宜。若離話筒太近，受講話氣流的影響，其低頻聲音會(huì)加重，聲音出現(xiàn)混雜不清、悶聲悶氣的效果，直接影響語(yǔ)言的清晰度，所以應(yīng)離話筒稍遠(yuǎn)一點(diǎn)兒，避免講話氣流直沖話筒;也不能太遠(yuǎn)，否則聲音信號(hào)會(huì)變?nèi)酰绊懯耙綮`敏度。另外，合適的距離能有效地抑制環(huán)境噪音的進(jìn)入。一般來(lái)說(shuō)，近場(chǎng)靈敏度要比遠(yuǎn)場(chǎng)高，而環(huán)境噪音都來(lái)自遠(yuǎn)場(chǎng)，如果演講者口型離傳聲器在10～20cm，發(fā)出的聲音屬于近場(chǎng)，演講者的低頻靈敏度比環(huán)境噪音高，從而相對(duì)抑制噪音靈敏度。

3. The distance between the microphone and the speaker. Generally speaking, the distance between the microphone used for speech and the mouth shape should be 10-20cm. If you are too close to the microphone, the low-frequency sound will worsen due to the influence of speech airflow, resulting in mixed and unclear sound, stuffy sound, and directly affecting the clarity of the language. Therefore, you should stay slightly away from the microphone to avoid speech airflow directed towards the microphone; It should not be too far, otherwise the sound signal will weaken and affect the pickup sensitivity. In addition, a suitable distance can effectively suppress the entry of environmental noise. Generally speaking, the near-field sensitivity is higher than the far-field sensitivity, and environmental noise comes from the far-field. If the speaker's mouth is 10-20cm away from the microphone, the sound emitted belongs to the near-field, and the low-frequency sensitivity of the speaker is higher than that of environmental noise, thus relatively suppressing noise sensitivity.