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语音信号处理技术是语音处理领域中新近发展起来的一个学科分支，而频谱分析技术是进行语音信号处理的基础。数字傅里叶变换（DFT）及快速傅里叶变换（FFT）是进行数字信号频谱分析的重要方法。MATLAB是一个功能强大的数据分析和处理工具，能够方便地实现语音信号的采集、分析和处理。本文将介绍在MATLAB环境中如何采集声音信号以及采集后的频谱分析方法，并使用MATLAB软件的GUI模块设计了一个简易的声音信号频谱分析仪。
随着信息时代的到来，数字信号处理已成为重要的技术领域，广泛应用于通信、语音、图像、自动控制、医疗和家用电器等多个领域。任何一个信号都具有时域与频域特性，信号的频谱完全代表了信号本身。因此，研究信号的频谱就等于研究信号本身。从频域角度对信号进行分析与处理，能够更深入地了解信号的特性。因此，信号的频谱分析是数字信号处理技术中一种较为重要的工具。
声卡是计算机最基本的配置硬件之一，价格便宜且使用方便。MATLAB工具箱集成了一些语音处理功能函数。本文将介绍基于声卡与MATLAB的声音信号频谱分析仪的设计原理与实现方法。
频谱分析通过傅里叶变换将波形 ( x(t) ) 变换为频谱 ( X(f) )，从而从另一角度了解信号特征。常见的傅里叶变换有DFT和FFT。DFT是FFT的基础，FFT是DFT的快速算法，在MATLAB中可以利用函数 fft 来计算序列的离散傅里叶变换DFT。FFT是时域和频域转换的基本运算。
function varargout = SpectrumAnalysis(varargin)% SPECTRUMANALYSIS: MATLAB code for SpectrumAnalysis.fig% SPECTRUMANALYSIS, by itself, creates a new SPECTRUMANALYSIS or raises the existing singleton.% H = SPECTRUMANALYSIS returns the handle to a new SPECTRUMANALYSIS or the handle to the existing singleton.% SPECTRUMANALYSIS('CALLBACK',hObject,eventData,handles,...) calls the local function named CALLBACK in SPECTRUMANALYSIS.M with the given input arguments.% SPECTRUMANALYSIS('Property','Value',...) creates a new SPECTRUMANALYSIS or raises the existing singleton*. Starting from the left, property value pairs are applied to the GUI before SpectrumAnalysis_OpeningFcn gets called. An unrecognized property name or invalid value makes property application stop. All inputs are passed to SpectrumAnalysis_OpeningFcn via varargin.% *See GUI Options on GUIDE's Tools menu. Choose "GUI allows only one instance to run (singleton)".% See also: GUIDE, GUIDATA, GUIHANDLES% Edit the above text to modify the response to help SpectrumAnalysis% Last Modified by GUIDE v2.5 02-Nov-2011 15:49:23% Begin initialization code - DO NOT EDITgui_Singleton = 1;gui_State = struct('gui_Name', mfilename, ... 'gui_Singleton', gui_Singleton, ... 'gui_OpeningFcn', @SpectrumAnalysis_OpeningFcn, ... 'gui_OutputFcn', @SpectrumAnalysis_OutputFcn, ... 'gui_LayoutFcn', [] , ... 'gui_Callback', []);if nargin && ischar(varargin{1}) gui_State.gui_Callback = str2func(varargin{1});endifnargout[varargout{1:nargout}] = gui_mainfcn(gui_State, varargin{:});else gui_mainfcn(gui_State, varargin{:});end% End initialization code - DO NOT EDIT% --- Executes just before SpectrumAnalysis is made visiblefunction SpectrumAnalysis_OpeningFcn(hObject, eventdata, handles, varargin)% This function has no output args, see OutputFcn.% hObject handle to figure% eventdata reserved - to be defined in a future version of MATLAB% handles structure with handles and user data (see GUIDATA)% varargin command line arguments to SpectrumAnalysis (see VARARGIN)handles.output = hObject;xlabel(handles.axes1,'Time (s)','fontweight','bold');xlabel(handles.axes2,'Frequency (Hz)','fontweight','bold');xlabel(handles.axes3,'Frequency (Hz)','fontweight','bold');ylabel(handles.axes1,'Amplitude','fontweight','bold');ylabel(handles.axes2,'Amplitude','fontweight','bold');ylabel(handles.axes3,'Amplitude','fontweight','bold');% Update handles structureguidata(hObject, handles);% UIWAIT makes SpectrumAnalysis wait for user response (see UIRESUME)uiwait(handles.figure1);% --- Outputs from this function are returned to the command linefunction varargout = SpectrumAnalysis_OutputFcn(hObject, eventdata, handles)% varargout cell array for returning output args (see VARARGOUT);% hObject handle to figure% eventdata reserved - to be defined in a future version of MATLAB% handles structure with handles and user data (see GUIDATA)% Get default command line output from handles structurevarargout{1} = handles.output;function edit_Fs_Callback(hObject, eventdata, handles)% hObject handle to edit_Fs (see GCBO)% eventdata reserved - to be defined in a future version of MATLAB% handles structure with handles and user data (see GUIDATA)% Hints: get(hObject,'String') returns contents of edit_Fs as text% str2double(get(hObject,'String')) returns contents of edit_Fs as a double% --- Executes during object creation, after setting all propertiesfunction edit_Fs_CreateFcn(hObject, eventdata, handles)% hObject handle to edit_Fs (see GCBO)% eventdata reserved - to be defined in a future version of MATLAB% handles empty - handles not created until after all CreateFcns called% Hint: edit controls usually have a white background on Windows.% See ISPC and COMPUTER.if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor')) set(hObject,'BackgroundColor','white');endfunction edit_TestA_Callback(hObject, eventdata, handles)% hObject handle to edit_TestA (see GCBO)% eventdata reserved - to be defined in a future version of MATLAB% handles structure with handles and user data (see GUIDATA)% Hints: get(hObject,'String') returns contents of edit_TestA as text% str2double(get(hObject,'String')) returns contents of edit_TestA as a double% --- Executes during object creation, after setting all propertiesfunction edit_TestA_CreateFcn(hObject, eventdata, handles)% hObject handle to edit_TestA (see GCBO)% eventdata reserved - to be defined in a future version of MATLAB% handles empty - handles not created until after all CreateFcns called% Hint: edit controls usually have a white background on Windows.% See ISPC and COMPUTER.if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor')) set(hObject,'BackgroundColor','white');endfunction edit_TestF_Callback(hObject, eventdata, handles)% hObject handle to edit_TestF (see GCBO)% eventdata reserved - to be defined in a future version of MATLAB% handles structure with handles and user data (see GUIDATA)% Hints: get(hObject,'String') returns contents of edit_TestF as text% str2double(get(hObject,'String')) returns contents of edit_TestF as a double% --- Executes during object creation, after setting all propertiesfunction edit_TestF_CreateFcn(hObject, eventdata, handles)% hObject handle to edit_TestF (see GCBO)% eventdata reserved - to be defined in a future version of MATLAB% handles empty - handles not created until after all CreateFcns called% Hint: edit controls usually have a white background on Windows.% See ISPC and COMPUTER.if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor')) set(hObject,'BackgroundColor','white');end 通过实验验证，本设计的语音信号频谱分析仪能够实现语音信号的采集与频谱分析。系统运行稳定，用户操作简单，能够直观地显示语音信号的频谱分布。实验结果表明，该工具能够有效地分析语音信号的频率成分，便于进一步的语音处理任务。
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