A promising start up in silicon valley Please send inquiry to mitbbs mail if interested. Thanks Electrical Engineer: Sunnyvale, Full Time Responsibilities Design of wearable eye tracking systems that include: cameras, illumination, efficient power supplies, processors Creating rapid prototypes and/or proof-of-concept models Hands on breadboarding and prototyping. Qualifications: Electrical Engineering degree Minimum 5 years commercial work experience, including several commercial product cycles. Ability to solder fine pitch electronics, manual wiring, alignment of optical components, PCB design, overseeing fabrication, testing. Electronics Technician: Sunnyvale, Full Time Responsibilities Surface mount hand-soldering Creating rapid prototypes and/or proof-of-concept models Creating and maintaining bill-of-materials Purchasing Qualifications: Associate of Science in Electronics Certifications: ISCET or ETA-I Min. 6 years experience as electronics technician (or Biomedical Technician) Ability to solder fine pitch electronics, manual wiring, alignment of optical components
所以我贴了一下那个计算器,呵呵。不论CD,SACD,LP,录音的时候麦克风都是主要在 20-20k里面的,回放的时候谐振对音色影响挺大。比如回放一个5000hz的高音 Overtones ▼ Harmonics Overwaves Partial tones Frequencies in Hz Partials Input: Fundamental frequency in 5000 Hz 1st harmonic
Solution: 1st overtone 10000 2nd harmonic 2nd overtone 15000 3rd harmonic 3rd overtone 20000 4th harmonic 4th overtone 25000 5th harmonic 5th overtone 30000 6th harmonic 6th overtone 35000 7th harmonic 7th overtone 40000 8th harmonic 8th overtone 45000 9th harmonic 9th overtone 50000 10th harmonic 10th overtone 55000 11th harmonic 11th overtone 60000 12th harmonic 12th overtone 65000 13th harmonic 13th overtone 70000 14th harmonic 14th overtone 75000 15th harmonic 15th overtone 80000 16th harmonic 从五次谐波开始就超过20000了,虽然录音和数字记录的时候不会呈现,但是在hifi系 统里回放的时候从dac,前级,后级,到喇叭,全都会有THD,到时候就被tannoy的超高 回放了不是?产生的谐波对于模拟录音现场的谐振是各有利弊的。单端胆机,胆dac, 不就是因为偶次谐波较多,对弦乐音色还原自然而吸引人么? 那个计算器网页写了一段: Typical "warm" tube sound, particularly triodes contain predominantly in the spectrum even-numbered multiples of the fundamental frequency, and thus outstanding even-numbered harmonics, or even-numbered partial tones 2, 4, 6… One can also say, tube amplifiers at high levels (distortion) contain strong odd-numbered overtones - that are even-numbered partials or harmonics. Organ pipes closed at the top (gedackt), which are half as long as open organ pipes of the same pitch, have a slightly dull and hollow sound. The spectrum shows predominantly odd-numbered multiples of the fundamental frequency and thus outstanding odd-numbered harmonics, or odd-numbered partial tones 3, 5, 7… One can also say, gedackt (covered, stopped) organ pipes, and also the clarinet contains mostly even-numbered overtones - that are odd-numbered partials or harmonics. Because a clarinet acts like a closed tube resonator, it theoretically produces only odd-numbered harmonics, that are even-numbered overtones. But there are also some even- numbered harmonics。
好坑。我继续跳。 好的脉冲响应,等同于宽的频域响应。 上面的文章分析得很彻底了,人耳的生理构造能分辨的时域分辨率在5微秒左右,换算 成频域,至少需要40k的频率响应和120分贝的动态范围才能重现5微秒的时域分辨率 ( 80k采样频率,20bit)。所以96k/24b 和192k/24b对声场的还原一定比44k/16b 的好。 我们的耳朵和大脑是最牛的hifi。 TO FULLY MEET the requirements of human auditory perception I believe that a sound system must cover the frequency range of about 15Hz to at least 40kHz (some say 80kHz or more) with over 120dB dynamic range to properly handle transient peaks and with a transient time accuracy of a few microseconds at high frequencies and 1°-2° phase accuracy down to 30Hz. This standard is beyond the capabilities of present day systems but it is most important that we understand the degradation of perceived sound quality that results from the compromises being made in the sound delivery systems now in use. The transducers are the most obvious problem areas, but the storage systems and all the electronics and interconnections are important as well.