Structural Design¶
What kind of microphone should be used for speech products?¶
Analog microphone or silicon microphone can be selected. In order to maintain good performance, our company recommends microphone specifications with sensitivity level of - 32 ± 3dB, and signal-to-noise ratio of >70dB. In addition, consider vibration around microphone. If there is no vibration, the microphone can generally use a thin rubber sleeve (usually with an outer diameter of 7MM); In case of vibration, it is recommended to use thick rubber sleeve (common outer diameter 10MM).
What should I pay attention to when installing the microphone?¶
When installing the microphone, ensure it faces the user’s speaking position to maximize the pickup range and avoid any obstructions. Take special care to minimize exposure to wind and air currents, and keep it away from noise sources and devices that may cause electromagnetic interference (such as motors).
The microphone must be fully inserted into the rubber sleeve with a secure and tight seal. Avoid any misalignment or incomplete insertion that prevents the microphone from reaching the bottom of the sleeve. It is recommended to use sealing material to seal the back of the microphone to prevent sound waves from entering through the rear, which could affect recognition performance.
How to design the microphone when designing the product structure?¶
When designing the structure of speech products, it is necessary to design installation holes for microphones. The installation hole should fit the external diameter of the selected microphone well, and it is better not to leave a gap. If the microphone opening inevitably leaves a gap, please ensure that the gap is symmetrical. If the gap on one side of the microphone is too large, it will seriously affect the microphone speech acquisition and speech recognition effect.
The product shell shall be designed with a audio pickup hole at the microphone. The pickup hole shall be located at the center of the microphone installation position as far as possible. The depth requirement: the diameter of the pickup hole shall be greater than 80% of the hole depth.
What should be paid attention to in the structure of dual microphone design?¶
For dual microphone products, it should be noted that the two microphones remain in the same direction, that is, the central axes of the two microphones are parallel and in the same direction. The distance between the two microphones shall be 3-8CM, that is, the central axis of the two microphones shall be 3-8CM.
If the noise reduction algorithm is applied, the required microphone distance of the noise reduction algorithm should also be verified.
Our current DOA (Direction of Arrival) implementation requires a fixed 4cm spacing between the two microphones. If you encounter structural design constraints, please contact our technical support for assistance.
How to improve the performance of acoustic echo cancellation in structure?¶
For products with AEC function, special attention should be paid to separating the microphone from the speaker during installation to prevent the sound broadcasted from the speaker entering into the microphone, affecting the performance of AEC.
What kind of speakers should be used for speech products?¶
The specific specifications of the speaker can be selected according to the product requirements and the specifications of the hardware board power amplifier. At present, our standard speech module hardware adopts a power amplifier with a basic specification of 8 Ω 2W. When using the existing amplifier, please select speakers with 8Ω impedance and 2W or lower power rating. If you choose to use a different amplifier, you may select other speakers based on the amplifier’s specifications.
What should be paid attention to when installing the speaker?¶
The speaker should be installed as far away from the microphone as possible, preferably facing the opposite direction of the microphone. For products with AEC function, take extra care to prevent direct sound transmission from the speaker to the microphone. We recommend keeping the speaker output below 95dB for products with echo cancellation.
How to design the speaker when designing the product structure?¶
During product structural design, it is recommended to pre-design the speaker’s sound outlet and mounting slot with proper enclosure to prevent sound reflection and propagation within the product structure, which could affect audio playback or recognition performance.
Additionally, considering the vibration produced by speakers, proper management of sound propagation and vibration transmission during operation is essential. Measures should be taken to prevent or minimize the transmission of speaker sound or vibration to the microphone, which could otherwise impact recognition accuracy.