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、扩声系统设计要求

2、 Design requirements for sound reinforcement systems

学校报告厅主要承担学术报告、会议等以语言为主的扩声，这就要求音响扩声系统能真实清晰地还原语言信号。，系统要保证有良好的语言清晰度和足够的、均匀的声压，语言清晰度频带在300～6000Hz。此外，报告厅也是进行歌舞、戏曲、音乐等文艺表演的场所，需要扩声系统能还原再现各种音源。因此，这就对信号的清晰度和丰满度提出更高的要求。

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、扩声系统的设计标准

3、 Design standards for sound reinforcement systems

音量的设计标准音量和扩声系统的额定功率相关，足够的音量是扩声系统的基础目标要求。根据行业标准GB50371—2006《厅堂扩声系统设计规范》对多功能用途扩声标准要求，以语言类为主的厅堂大声压为≥90dB，一舞厅≥103dB，二舞厅≥110dB。音量水平是根据信噪比和系统运行特色来决定的。

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.

音质的设计标准音质主要取决于扩声系统的非线性失真和传输频率特性。国标规定一厅堂传输频率特性指标为以100～6300Hz的平均声压为0dB，在此频带内允许范围为-4～+5dB，50～100Hz和6300～12500Hz的允许范围为-8～+4dB。频率传输特性是决定音质的关键指标，非线性失真也是影响音质效果的因素之一。此外，音乐和语言的清晰度也是衡量音质的重要标准。清晰度的衡量方法很多，实际操作中通常依靠现场的主观感觉进行评价。

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.

声场的设计标准标准要求一厅堂不均匀度为1000Hz时不大于6dB，4000Hz时不大于8dB，100Hz处不大于10dB。所以，学校报告厅应该按照标准来构建声场，要求有尽可能均匀的声场。

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、传声器的选择和应用

4、 Selection and application of microphones

传声器是整个系统的“入口”。传声器把采集到的声波信号转变成微弱的电压信号进行输出，这就需要后端的音频处理设备把信号放大提高，因此，如果话筒有杂音输入，那么后端很难，传声器的选择和使用方法对扩声质量和效果会产生很大影响。此外，在室内存在声反馈的矛盾，因此，对传声器(话筒)的灵敏度、频响范围、指向性都有较高的要求。

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).

灵敏度是指传声器开路输出电压U和声压P的比值。实际上并不是灵敏度越大越好，灵敏度适中就可，不一定追求高灵敏度。传声增益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.

对室内扩声来说，扩声系统所能达到的声音大小程度受声反馈(反馈就是声音从扬声器经功放音箱输出再传回扬声器的过程。经多次反馈达到一定时，啸叫便会产生)的牵制。因此，在同一扩声系统中，传声器灵敏度高了，输出电压就会增大，扬声器发出的声音也会相应增大。为了防止反馈啸叫，不得不把音量调小，从而达到良好的扩声效果。

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.

频响范围是指传声器在一恒定声压下，不同频率时测得的输出电压变化值。一般来说，频响曲线越平越好，对于会议话筒，其频响范围在250～4000Hz就可以了。设计时应将频谱范围放在较高的频段内，以提高语言的清晰度。因为人的语言频谱范围一般在100～4000Hz，所以对清晰度影响较大的是高频段。

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.

传声器的指向性是指在某一频率下，在某一方向的灵敏度与大灵敏度的比值。对于学术报告、会议等语言类扩声来说，为有效地预防、抑制声反馈引起的声音啸叫，要选用有指向性的传声器。指向性与接受的声波信号频率有很大关系：频率越低时，指向性越差;频率越高时，指向性越强。

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.

输出阻抗是传声器输出端用频率1kHz声音信号测得的内阻的模值，分为高阻抗和低阻抗两种。我国使用的是200Ω、600Ω和2000Ω。传声器具体有以下应用。

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。对于传声器的拾音方式主要分为两种情况：在进行语言扩声时，话筒的声轴要正对演讲人;而在进行音乐会的扩声时，一般采取立体拾音的方式来进行。

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、相对位置。距离越大越能减少声反馈，因此，话筒在摆放时相对位置要远，应该尽量降低高度并避免其正对音箱。

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、传声器与发声者的距离。一般来说，用作演讲的话筒离口型的距离取为10～20cm为宜。若离话筒太近，受讲话气流的影响，其低频声音会加重，声音出现混杂不清、闷声闷气的效果，直接影响语言的清晰度，所以应离话筒稍远一点儿，避免讲话气流直冲话筒;也不能太远，否则声音信号会变弱，影响拾音灵敏度。另外，合适的距离能有效地抑制环境噪音的进入。一般来说，近场灵敏度要比远场高，而环境噪音都来自远场，如果演讲者口型离传声器在10～20cm，发出的声音属于近场，演讲者的低频灵敏度比环境噪音高，从而相对抑制噪音灵敏度。

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.