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 as sensitivity level - 32 ± 3dB, and signal-to-noise ratio>70dB. In addition, consider whether there is vibration in the installation position of the product 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, please try to face the user’s speech position as far as possible, and the installation position should expand the pickup range as far as possible to avoid blocking. Special attention shall be paid to avoiding the influence of wind and air flow as far as possible, and keeping away from noise sources and devices (such as motors) that are easy to cause electromagnetic interference.
When installing the microphone, it shall be completely inserted into the rubber sleeve, and the sealing shall be firm and tight to avoid oblique installation and microphone not inserted into the bottom of the rubber sleeve. It is recommended to seal the back of the microphone with sealing materials to prevent the sound wave from entering the microphone and affecting the recognition effect.
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 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 of double microphone correlation is added, the microphone distance parameter of the noise reduction algorithm should also be checked for matching with the actual installation distance.
In addition, if the TDOA (sound source positioning) function is required, the left and right microphones shall be distinguished during installation, and the installation cannot be switched.
Our current TDOA (sound source positioning) function requires that the distance between two microphones is 4cm. In case of structural design difficulties, please contact our technical support personnel for help.
How to improve the performance of echo cancellation in structure?¶
For products with echo cancellation function, special attention should be paid to separating the microphone from the speaker during installation to prevent the sound from the speaker from entering the microphone closely, which will affect the performance of echo cancellation.
What kind of speakers should be used for speech products?¶
The specific specifications of the loudspeaker 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. Without changing the power amplifier, please select speakers with a power amplifier of 8 Ω 2W or less. Other speakers can be selected according to the specifications of the power amplifier when the power amplifier is selected.
What should be paid attention to when installing the horn?¶
The speaker should be installed as far away from the microphone as possible, preferably facing away from the microphone. For products with echo cancellation, special attention should be paid to avoid the sound from the speaker directly entering the microphone. It is recommended that the output sound of the product horn with echo cancellation function should not exceed 95dB.
How to design the horn when designing the product structure?¶
During the product structure design, it is recommended to design the sound outlet and installation slot of the horn in advance. It is better to have a certain sealing effect to avoid the sound of the horn from reflecting and propagating inside the product structure, which will affect the playback or recognition effect.
In addition, considering the vibration of the loudspeaker, sound transmission and vibration transmission during loudspeaker playing should also be handled properly. Avoid or reduce the speaker sound or vibration to the microphone and affect the recognition effect.