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Product Structure Design

Microphone structure design

Voice and communication characteristics

  1. The concept of vibration: a generalized definition of vibration in physics: all physical processes that periodically and repeatedly change with time are collectively referred to as “vibration”. To put it simply, the back and forth movement of particles or objects is called “vibration”, which is a way of energy transmission;
  2. Sound generation: When one or more particles vibrate, they drive the surrounding particles to vibrate. In the process of such vibration (object vibration), air vibration is caused to generate energy waves (including infrasound waves, acoustic waves, and ultrasonic waves). The vibration waves that can produce human hearing are called sound waves. Its acoustic frequency is within the frequency range of about 20-20000Hz;
  3. Speech is the transmission of human language using sound waves. Language+sound wave=speech. Speech recognition is to recover and demodulate language from speech.

语音及传播特点

Microphone selection suggestions

  1. Select analog microphone with sensitivity of - 32 ± 3dB; If the signal-to-noise ratio is>70dB, you can refer to the models in ☞Microphone Compatibility List for selection;
  2. Select single microphone or dual microphone scheme according to the function, and contact our technicians for specific selection;
  3. Common microphones are 7 or 10mm rubber sleeves. Common products are 7MM rubber sleeves. If there is vibration during operation, it is recommended to use 10MM rubber sleeves. Basic specifications such as interface, line length, etc. shall be selected according to specific requirements.

Suggestions on microphone opening structure design

  1. The microphone inlet must be designed; The diameter of the pickup hole is related to the hole depth (housing thickness).

  2. It is better to place the microphone hole on the front of the product, facing the user, to ensure the maximum range of pickup, and avoid other materials blocking the microphone;

  3. Waterproof and dust-proof microphones shall be considered for microphone location. If there is water or dust in the use environment, waterproof and dust-proof microphones shall be selected;
  4. Keep away from water inlet and outlet, air inlet and outlet, machinery, horn, electromagnetic, strong current and other noises that affect speech. The decibel meter will have better recognition effect if the steady noise at the microphone is less than 60dB during product testing;
  5. Microphone mounting holes or slots must be designed; It should match the outer diameter of the microphone sleeve, 7 or 10mm rubber sleeve (due to the difference of each rubber sleeve, note that the size of the microphone opening slot should be confirmed with the microphone manufacturer, generally the hole slot is smaller than 0.1-0.2MM of the overall microphone diameter);
  6. It is necessary to consider the convenient layout of microphone cable, which should be far away from strong electricity and avoid being bundled with strong electricity;
  7. The recommended distance between two microphones is 4CM (the center distance between two microphones). If you have other distance requirements, you can communicate with our FAE;
  8. With AEC function, the microphone shall be as far away from the speaker as possible, the speaker sound at the microphone shall not exceed 83DB, and the speaker output sound shall not exceed 95DB;
  9. It is recommended to communicate with our technicians for confirmation before opening the structure;
  10. It is better not to have a cavity between the pickup hole and the microphone. It can be changed to a plum shaped hole according to the appearance.

Microphone installation suggestions

  1. The microphone must be fixed firmly and cannot be loosened, otherwise the recognition effect will be affected;
  2. Select RTV silica gel that meets the environmental RoHS requirements. The recommended common silica gel is 703/704/737 or other organic materials;
  3. Insert the microphone completely into the fixing hole to avoid deflection, and align the center hole of the pickup hole with the center of the microphone;
  4. The thickness of silicone sealant is less than 3mm, and the full curing at real temperature is generally 8-12H. The curing time is longer when it is greater than 3mm. It can be poured in layers for many times to ensure full curing, stability and sealing. The fixed microphone process can be advanced during production;
  5. It is prohibited to directly apply hot sol to fix the microphone head. The microphone wiring is pulled by gravity, which may cause the microphone to be pulled askew before it is fully solidified. Also, pay attention to fixing the microphone plug cable.

Structural design of horn

Speaker introduction and selection

  1. The module board or power amplifier circuit of our company can be selected by referring to the models in ☞Speaker Compatibility List;
  2. For automatic design, speakers of different specifications can be selected according to the output power;
  3. If the function of AEC (echo cancellation) is provided, speakers with sound chambers should be selected. The THD output distortion should be less than 10% at the maximum volume of 150HZ-3000HZ.

Structural design of horn

  1. The speaker outlet is far away from the microphone, and the location can be selected according to the microphone structure design;
  2. Loudspeakers shall be designed with sound holes, and round holes are recommended. Common design shapes are: round, circular arc, square, triangle;

  3. The aperture of the sound outlet is recommended to be 1mm. The aperture range is 0.8-1.5mm, and it should not be less than 0.5mm. Too small is not conducive to sound, and the sound is small and thin;

  4. The area of the sound outlet is generally between 5% and 15% of the vibration area of the horn diaphragm, and 10% is recommended. The sound volume and quality are both good. Too much high frequency noise may be caused, and too little noise may be caused.

Basic requirements for horn structure installation

  1. The horn must be fixed firmly and cannot be loosened, otherwise the sound production effect will be affected;
  2. Put the speaker into the fixed slot completely to avoid deflection, and align the center hole of the pickup hole with the center of the microphone.