**I. Project Overview**
1.1 Introduction
With the rapid growth of industrial production, transportation, urban development, and population density, the increase in household appliances such as audio systems, air conditioners, and televisions has led to a significant rise in environmental noise. This has become one of the major forms of public pollution, affecting both human health and the quality of life. As a result, the monitoring of environmental noise has become an essential concern for governments, researchers, and communities alike. A real-time noise spectrum analyzer is a critical tool used for measuring and analyzing noise signals. It is widely utilized in professional noise monitoring, acoustic research, and various applications that require accurate sound analysis.
Traditional analog spectrum analyzers have several limitations, including complex hardware design, inability to capture phase information, and lack of real-time processing capabilities. These devices are often bulky, difficult to transport, and not suitable for dynamic or complex noise environments. In contrast, modern spectrum analyzers based on Fast Fourier Transform (FFT) provide a more efficient and accurate way to analyze noise signals. They use digital signal processing techniques to convert input signals into discrete frequency components through FFT operations, offering better resolution and flexibility. The system samples the input signal via an Analog-to-Digital Converter (ADC), processes it using FFT, and generates a visual representation of the noise spectrum, making it ideal for real-time noise monitoring and analysis.
1.2 Project Background / Motivation
This project utilizes the AVR EVK1105 development kit, which is built around the AT32UC3A0512 microcontroller. This chip offers a powerful fixed-point computing capability, a built-in hardware multiplier, and support for DSP instructions, making it well-suited for digital signal processing tasks. Additionally, the EVK1105 includes the TLV320AIC23B low-power stereo audio codec, which supports both microphone and line-in inputs, along with programmable gain control for both input and output. It also provides 16-bit ADC conversion at sampling rates up to 96 kHz, ensuring high precision in data acquisition. The board is equipped with a QVGA (320x240) full-color LCD display, allowing for clear visualization of waveforms and spectra, as well as a user-friendly interface.
By leveraging the hardware and software resources of the AVR EVK1105, this project implements a real-time noise spectrum analyzer that can be controlled via Wi-Fi. The system uses digital signal processing techniques, including FIR filtering and FFT, to extract the spectral characteristics of noise signals. It also calculates key noise parameters and displays them in real time. The addition of Wi-Fi connectivity enables remote control, making it suitable for unattended environments where manual operation is impractical. The device is compact, easy to use, and portable, making it ideal for field measurements and long-term monitoring tasks.
**II. Requirements Analysis**
2.1 Functional Requirements
1) Real-time measurement and display of noise signal parameters:
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) weighted by A, C, and Z scales.
- Maximum, minimum, and peak sound pressure levels (with A and C weighting).
- Equivalent continuous sound pressure level (Leq) under A and C weighting.
- Cumulative percentage sound levels (Ln) with A and C weighting.
2) Implement wireless control via Wi-Fi for remote operation, enabling noise measurement in unmanned settings.
3) Support data storage and playback via an SD card for later analysis.
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 Implementation Principle
The system acquires noise signal data through the audio input interface or microphone of the AVR EVK1105 development board. The TLV320AIC23B audio codec performs 16-bit ADC conversion, transforming the analog signal into a digital format. The AT32UC3A0512 microcontroller then processes the data using its built-in DSP instruction set, applying FIR filtering and FFT algorithms to generate the frequency spectrum of the noise signal. The system calculates relevant parameters and displays them in real time on the QVGA LCD screen, showing waveforms, spectrograms, and numerical values. Collected data can also be stored on an SD card for future playback and detailed analysis.
The system further supports Wi-Fi connectivity, allowing users to remotely control the device. This includes setting measurement parameters, starting or stopping measurements, and accessing real-time data from a distance. Such features make the system highly adaptable for use in unattended environments, where manual intervention is not feasible. By combining real-time signal processing with wireless communication, the system effectively fulfills the requirements for comprehensive 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. This platform provides a robust foundation for digital signal processing tasks. The EVK1105 includes the following hardware resources:
- AT32UC3A0512 microcontroller with DSP capabilities.
- TLV320AIC23B audio codec for high-quality ADC/DAC conversion.
- QVGA full-color LCD for real-time visualization.
- SD card slot for data storage and playback.
- Wi-Fi module for remote control and communication.
These components work together to ensure the system meets all functional and performance requirements while maintaining a compact and user-friendly design.
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