Harmony-Central网站的论坛上有一位wetwareinterface先生发一个帖子，想考考大家有关合成器的常识。跟帖很踊跃，但是大部分跟帖水平不高。下面是他提出的10个问题，也请大家考考自己。

     原文的网址如下，有兴趣的朋友可以直接参加讨论。

     http://acapella.harmony-central.com/forums/showthread.php?threadid=243252
    
     10个有关合成技术的测验题

     1. Describe the differences between the concepts of Frequency Modulation and Ring/Amplitude Modulation, and briefly, but accurately, define each. 2 points

     2. What is a Sawtooth waveform. 1 point

     3. What is a Pulse waveform. 1 point

     4. What is a Square waveform. 1 point

     5. Describe how to generate a Square wave using Additive synthesis principles, and then with FM. 6 points

     6. A Low Pass Filter does what to an audio signal. 2 points

     7. Of the three synthesis methods listed; Additive, Subtractive, and FM which would be the closest description of a 440 hz sine wave with a delay placed on it timed at 2.27 ms and a feedback ratio of 33 %. 1 point

     8. Of the three synthesis methods listed; Additive, Subtractive, and FM which would be the closest description of a 440 hz sine wave with a delay placed on it timed at 2.27 ms and a feedback ratio of 20 %. 1 point

     9. If you mix a sine wave at a frequency of 440 hz with another one 180 degrees out of phase at 220 hz and both have an amplitude of 60 db, what would be the resultant frequency and amplitude measured in hz and db? 4 points

     10. what is White noise 1 point

     1）请叙述频率调制和环形/幅度调制之间的不同，给它们二者下一个简明而准确的定义。（2分）

     2）什么是锯齿波？（1分）

     3）什么是脉冲波？（1分）

     4）什么是方波？（1分）

     5）请讲解怎样用加法合成和FM合成发生方波（6分）

     6）低通滤波器对音频信号做些什么？（2分）

     7）加法、减法、调频三种合成方式中哪一种对延迟2.27ms，反馈率33%的440Hz正弦波描绘最为接近？（1分）

     8）加法、减法、调频三种合成方式中哪一种对延迟2.27ms，反馈率20%的440Hz正弦波描绘最为接近？（1分）

     9）将一个440Hz的正弦波和另一个相位差180度的220Hz正弦波混合，二者幅度都是60db，混合后的频率和幅度是多少？（4分）

     10）什么是白噪声？（1分）