Digital Voice Recorder

Overview

A digital voice recorder turns sound into files. Two MEMS capsules in the Microphone Array pick up the room, a Mainboard digitizes and encodes the signal, and the result is written to flash. The rest of the device is a Display Assembly to show levels, a Button Panel to drive it, a small Speaker and headphone jack for playback, and a LiPo Cell-based Battery Pack so it runs without mains power, all inside a pocketable Enclosure.

The design problem is capturing clean audio in a tiny case. The Microphone Array mounts its MEMS Microphone capsules on a Mic Isolation Mount so handling noise does not reach them, and a Windscreen tames wind and plosives. A Port Board adds USB-C and a microSD slot so recordings move off the device easily.

How it works

Each MEMS Microphone is a silicon membrane whose capacitance changes with sound pressure; its built-in preamp outputs an analog signal that the Audio ADC on the mainboard samples, clocked by the Audio Clock Crystal so the sample rate stays accurate. The Microcontroller takes that digital stream, applies gain and optional noise gating, and encodes it to WAV or MP3.

Files are written to the NAND Flash or to a card in the microSD Slot, with a FAT filesystem so a computer can read them directly over the Port Board USB-C link. While recording, the Microcontroller drives a level meter and timer on the LCD Panel of the Display Assembly, and the transport keys on the Button Panel move through files. The Record Slide Switch arms and starts capture in one motion, which is faster and quieter than a soft button.

Power comes from the Battery Pack: a single LiPo Cell guarded by a BMS Board that prevents over-discharge and manages charging from USB-C. For playback the Microcontroller decodes a file back through a DAC to the Headphone Jack for headphones or the internal Speaker, so you can check a take in the field without extra gear.