**I. Project Overview**
1.1 Introduction
With the rapid development of industrial production, transportation, urban construction, and increasing population density, the number of household appliances such as audio systems, air conditioners, and televisions has significantly risen. This has led to a growing concern over environmental noise pollution, which has become one of the most serious public issues affecting human society. As a result, the monitoring of environmental noise has gained widespread attention. A real-time noise spectrum analyzer is an essential tool for measuring and analyzing noise signals, commonly used in professional noise monitoring and audio signal research. Its applications are extensive due to its ability to provide detailed spectral analysis.
Traditional analog audio spectrum analyzers have several limitations, including complex hardware design, inability to capture phase information, and lack of portability. These devices are not suitable for real-time measurements in complex environments. In contrast, modern spectrum analyzers based on Fast Fourier Transform (FFT) decompose the input signal into discrete frequency components, enabling accurate spectral analysis. These digital analyzers use an Analog-to-Digital Converter (ADC) to directly sample the input signal, then apply FFT algorithms to generate a visual representation of the noise spectrum. This approach allows for more efficient and accurate noise analysis.
1.2 Project Background / Motivation
This project utilizes the AVR EVK1105 development kit, which is based on the AT32UC3A0512 microcontroller. The board features a built-in hardware multiplier, supports DSP instructions, and has 64KB of SRAM, making it well-suited for digital signal processing tasks. Additionally, the EVK1105 includes the TLV320AIC23B low-power stereo audio codec, which offers flexible input options (MIC and LINE IN) and programmable gain control for both input and output. It also provides high-accuracy 16-bit sampling at frequencies up to 96kHz, ensuring precise data acquisition.
The system features a QVGA (320x240) full-color LCD display, which effectively visualizes noise waveforms and spectra, along with a user-friendly interface. By leveraging the hardware and software resources of the EVK1105, this project implements a real-time noise spectrum analyzer that uses Wi-Fi for remote control. The device employs FIR filtering and FFT algorithms to process real-time noise signals, extract key parameters, and display them on the screen. It also includes Wi-Fi connectivity for unattended operations and an SD card slot for data storage and playback. The compact size, ease of use, and portability make it ideal for field applications.
**II. Requirements Analysis**
2.1 Functional Requirements
1) Real-time measurement and display of noise signals:
a) Display the real-time waveform of the noise signal.
b) Show the octave and 1/3 octave spectrum of the noise.
c) Measure key parameters, such as:
- Sound pressure level (Lp) with A, C, and Z weightings.
- Maximum, minimum, and peak sound pressure levels (with A and C weightings).
- Equivalent continuous sound pressure level (Leq) with A and C weightings.
- Cumulative percentage sound levels (Ln) with A and C weightings.
2) Implement Wi-Fi-based wireless communication for remote control and monitoring in unattended environments.
3) Support SD card for data storage and playback.
4) Include acoustic calibration using a sound calibrator for accuracy.
2.2 Performance Requirements
(1) Measurement range: 30–120 dB.
(2) Octave bandwidth: 31.5–16 kHz.
(3) 1/3 octave bandwidth: 20 Hz–20 kHz.
(4) Frequency resolution: 20 Hz.
**III. Program Design**
3.1 System Function Realization Principle
The system acquires noise signal data through the audio input or microphone on the AVR EVK1105 development board. The TLV320AIC23B audio codec performs 16-bit ADC conversion, transforming analog signals into digital data. The AT32UC3A0512 microcontroller then processes this data using its DSP instruction set, applying FIR filtering and FFT algorithms to obtain the frequency spectrum of the noise. The system displays real-time waveforms, spectrograms, and calculated parameters on the QVGA LCD screen.
Collected data can be stored on an SD card for later playback and analysis. The system also supports Wi-Fi connectivity, allowing remote operation such as setting measurement parameters and initiating measurements. This enables the device to function efficiently in unattended environments, fulfilling the requirements for real-time noise monitoring and analysis.
3.2 Hardware Platform Selection and Resource Configuration
1. Hardware Platform:
The system is built around the AVR EVK1105 development board, which is based on the AT32UC3A0512 microcontroller. The board provides a powerful platform for digital signal processing with its built-in hardware multiplier, DSP support, and ample memory.
The EVK1105 includes the following hardware resources:
- AT32UC3A0512 microcontroller with 64KB SRAM.
- TLV320AIC23B audio codec for high-quality audio input and output.
- QVGA (320x240) full-color LCD for visualization.
- SD card slot for data storage.
- Wi-Fi module for remote control and communication.
These components collectively ensure that the system meets the functional and performance requirements for real-time noise spectrum analysis.
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