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Conference rooms are hostile to microphones: speakers sit anywhere from half a meter to four meters away, HVAC and projectors add constant noise, and people turn their heads mid-sentence. A single microphone can only be acceptable in one direction no matter where you place it. MVSILICON's BP2668Dx, with four 32-bit ADCs at SNR ≥105 dB sampling in lockstep, makes a full omnidirectional array practical at a mainstream cost. This article covers the physics of array pickup, the chip-side requirements, and the design trade-offs that matter most.
Meeting rooms are acoustically unforgiving. A speaker may sit at either end of a long table, anywhere from half a meter to four meters from the microphone. Air conditioning, projectors, and laptop fans form a continuous noise floor. People turn their heads and shift in their seats. A single microphone delivers an acceptable direct-to-reverberant ratio in exactly one direction—sit at the far end and the voice turns dull and hollow.
An array trades space for directivity. By capturing with several microphones at once and processing the time differences at which sound reaches each capsule, the system can steer its pickup beam electronically toward whoever is speaking while suppressing reverberation and noise from other directions. That is beamforming, and it is the foundation of every modern conferencing terminal. Without an array, far-field pickup can only be achieved by raising gain—which raises the noise along with it.
Beamforming rests on delay estimation. When the same sound reaches two microphones separated by distance d, the arrival time difference depends on the angle between the source direction and the microphone axis: zero for on-axis incidence, maximal for side incidence. The system applies different delays to each channel and sums them, so sound from the target direction adds in phase and is reinforced while other directions partially cancel.
This mechanism produces two hard design constraints. The first is array aperture: a larger aperture yields better low-frequency directivity. The second is microphone spacing: once spacing exceeds half a wavelength at the highest frequency of interest, spatial aliasing sets in and the beam direction becomes ambiguous. Conferencing needs to cover speech intelligibility up to roughly 8 kHz, so spacing and aperture must be balanced between low-frequency directivity and high-frequency aliasing. That is precisely why ring arrays distribute capsules evenly around a fixed diameter.
Array algorithms impose one non-negotiable requirement on the analog front end: the ADCs must sample synchronously. If sampling instants drift between channels, the inter-channel phase difference no longer maps uniquely to source direction, and the beam will jitter or lock onto the wrong angle. The BP2668Dx provides four 32-bit ADCs at SNR of at least 105 dB, sampling four microphones from a common clock and giving downstream delay estimation a stable phase reference.
That 105 dB SNR matters especially in far-field pickup. With a speaker four meters away, the level reaching the capsule may be only around ten decibels above the ambient noise floor. Every few decibels of front-end SNR translates into usable dynamic range for the algorithms, which is what makes speech enhancement and acoustic echo cancellation behave reliably. In addition, the BP2668Dx's 39 GPIOs and 30-channel SAR-ADC can directly handle mute buttons, status LEDs, and touch detection, reducing external component count.
First, microphone selection and matching. Array algorithms assume highly consistent sensitivity and frequency response across channels, so MEMS capsule batch consistency directly affects beam quality. Channel pairing must be verified before the design is frozen. Second, enclosure openings. If a capsule is blocked or coupled into a narrow cavity, it introduces frequency ripple and phase distortion; port dimensions and acoustic damping need to be co-simulated with the mechanical design. Third, echo cancellation coordination. A conferencing terminal also plays audio, and the loudspeaker-to-microphone coupling path changes with the room. AEC must work together with the beamformer output—applying beam suppression before AEC generally outperforms the reverse order.
Q: How many microphones does an omnidirectional conferencing array need?
A: Three to eight is typical. More capsules sharpen directivity but demand more synchronous ADC channels and more DSP compute. A four-capsule ring array covers small and medium meeting rooms well.
Q: Why must the ADCs sample synchronously?
A: Beamforming locates sources from inter-channel phase differences. Unsynchronized sampling instants add phase error that the algorithm cannot compensate for, causing beam jitter or mis-steering.
Q: Can the BP2668Dx's four ADCs drive a four-microphone array directly?
A: Yes. Four 32-bit ADCs sample from a common clock at SNR ≥105 dB, matching a four-capsule ring array front end without external multi-channel ADCs.
Shenzhen Liwei Electronics Technology Co., Ltd. specializes in audio headset electronic solution design, offering one-stop services from chip selection to complete PCBA solutions. With 12 years of industry experience serving 15+ well-known brands and 300+ clients, Liwei has built proven designs on the MVSILICON BP26 platform across conferencing array pickup, broadcast audio processing, instrument effects, and digital mixing consoles, with full support from front-end array design through AEC tuning. Request a Quote for a tailored audio solution.
Shenzhen Liwei Electronics Technology Co., Ltd. specializes in audio headset electronic solution design, offering one-stop services from chip selection to complete PCBA solutions. With 12 years of industry experience serving 15+ well-known brands and 300+ clients, Liwei has built proven designs on the MVSILICON BP26 platform across conferencing array pickup, broadcast audio processing, instrument effects, and digital mixing consoles. Request a Quote for a tailored audio solution.
Keywords: MVSILICON BP2668Dx, conferencing microphone array, beamforming, omnidirectional pickup solution, BP26 conferencing audio solution
