Physics 4060, Acoustics Laboratory

Musical sound is characterized by pitch, loudness, and quality. Pitch is frequency. The loudness of a given sound is determined by its intensity (power per unit area) factored by the sensitivity of the ear for that frequency. Quality or timbre refers to those sound characteristics which allow a person to distinguish sounds which have identical pitch and loudness. These distinguishing characteristics include harmonic content, vibrato, and attack/decay transients.

音乐声由音调、响度和品质决定。音调是频率。某一声音的响度由其强度（单位面积上的功率）乘以人对这一频率的灵敏度来决定。品质或音色指的是那些使人们能够区分具有相同音调和响度的声音的声学特性。这些区分特性包括谐波成分、震颤和起音/衰减瞬态。

For sustained tones, the harmonic content is the dominant characteristic - and the determination of harmonic content is the point of this laboratory. To be more specific, "harmonic content" refers to the sound spectrum:the frequencies and relative intensities of the higher frequencies present in the sound, expressed as a fraction or percent of the intensity of the fundamental component. The fundamental is defined as the lowest resonant frequency of the vibrating object which produces the sound, and the terms overtone and harmonic are used to describe other, higher frequencies present in the sound. Overtone is the more general term, referring to any frequency component above the fundamental, but most overtones in musical sound are harmonics (integer multiples of the fundamental). Hence, determination of the sound spectrum usually involves identifying the harmonics and their relative intensity.

对于持续音调，谐波成分是主要特征——而本实验的要点就是确定谐波成分。更具体地说，‘谐波成分’指的是声音的频谱：声音中存在较高频率的频率及其相对于基频强度的相对强度，以基频强度的分数或百分比形式表示。基频定义为产生声音的振动物体的最低共振频率，而术语泛音和谐波用于描述声音中存在的其他较高频率。泛音是更通用的术语，指任何高于基频的频率成分，但音乐声音中的大多数泛音都是谐波（基频的整数倍）。因此，确定声音频谱通常涉及识别谐波及其相对强度。

The first step will be to produce a tape recording of sounds for analysis. Then the sounds will be analyzed by two different methods: (1) A/D Conversion with a Universal Laboratory Interface and the use of the Sound software accompanying it and (2) A/D conversion and discrete Fourier Analysis using the MacScope A/D Converter. As a final step, you will be given a pre-recorded sound which is supposed to contain only odd harmonics (characteristic of a cylinder with one end closed.) Your task is to analyze that sound, and then resynthesize it using a Fourier synthesizer and compare the sound of your synthesized version with the original.

第一步将是制作一份用于分析的声音磁带记录。然后，声音将通过两种不同的方法进行分析：(1) 使用通用实验室接口和其配套的Sound软件进行A/D转换；(2) 使用MacScope A/D转换器进行A/D转换和离散傅里叶分析。最后一步，你将获得一段预录制的声音，该声音仅包含奇次谐波（这是封闭端气柱的特征。）你的任务是分析这段声音，然后使用傅里叶合成器重新合成它，并将合成后的声音与原始声音进行比较。

Each person will be responsible for recording three sounds. You may bring a musical instrument if you wish, in which case you should record three different notes for the instrument at approximately the same dBA level. The sounds should be sustained as long as possible to facilitate analysis. Make note of the instrument used and the pitch if known ( i.e., concert pitch by frequency or letter name.) Alternatively you should use voiced vowel sounds. Select well defined vowel sounds and produce three sounds at about the same pitch and dBA level. It is helpful to think of a word and then sustain the vowel sound in that word. For example "AH" as in HOD, "EE" as in HEED and "OO" as in WHO'D.

每个人将负责录制三个声音。如果您愿意，可以携带一件乐器，此时应为该乐器录制三个不同音符，且在大约相同的dBA电平下进行。声音应尽可能持续，以方便分析。请记录所使用的乐器以及已知的音调（即，以频率或字母名称表示的音乐会调）。或者，您也可以使用元音辅音声音。选择清晰定义的元音声音，并在大约相同的音调和dBA电平下录制三个声音。设想一个单词，然后在该单词中持续元音声音。例如，用“AH”如在“HOD”中，用“EE”如在“HEED”中，用“OO”如在“WHO'D”中。

II. 使用通用实验室接口进行声音分析

In this section of the experiment, you will make use of a sound capture routine with a microphone an the ULI. The steps required are

在本实验部分，你将使用ULI上的麦克风进行声音采集。所需步骤为

1. Run the Sound program for the ULI on one of the laboratory computers. Prepare it to capture a sound signal as follows:

在实验室的一台电脑上运行ULI的Sound程序。准备它以捕获声音信号，方法如下：

a. Turn off the repeat mode: Use the mouse to position the arrow over Collect at the top of the screen. A menu should appear. Holding the mouse button down, move the pointer down to Repeat Mode and if there is a check mark beside Repeat Mode, release the mouse button there to take off the check. If there is no check, then Repeat Mode has already been turned off, so you should move the pointer back to the top of the screen before releasing the mouse button.

关闭重复模式：使用鼠标将箭头定位到屏幕顶部的Collect。应出现一个菜单。按住鼠标按钮，将指针向下移动到Repeat Mode，并如果Repeat Mode旁边有勾选标记，就在那里释放鼠标按钮以取消勾选。如果已经没有勾选标记，则说明Repeat Mode已关闭，因此在释放鼠标按钮前应将指针移回到屏幕顶部。

b. Choose "One Graph" from the Display menu by the same kind of procedure used above, i.e., display the menu and move the pointer over "One Graph" and release the mouse button.

b. 通过与上述相同的方式从显示菜单中选择'一个图'，即显示菜单并将指针移到'一个图'上然后释放鼠标按钮。

2. Put the microphone of the ULI within a few centimeters of one of the loudspeakers of the sound console so that the produced sound from your tape will be strong compared to room background noise.

将ULI的麦克风置于声音调音台的一个扬声器前方几厘米处，使录音带产生的声音比房间背景噪声要大。

3. Play your tape and get a satisfactory sound level from the speaker. With your first sound playing, click start on the computer screen to capture a sound sample. A single sample will be collected at that time, but it will be a few seconds before it is displayed. Scale the waveform as necessary to see whether it is satisfactory and repeat if necessary.

播放录音带，从扬声器获得满意的声电平。在第一次声音播放时，点击计算机屏幕上的“开始”按钮以捕获一个声音样本。此时将收集到一个样本，但需要几秒钟才能显示出来。根据需要调整波形的刻度，以确定是否满意，并在必要时重复操作。

4. Save the sound sample on your disc with a name which will identify it clearly - you will have to find it for the analysis. To save it, choose "Save Experiment as.." from the File menu. You will be prompted for a name, but after typing the name you must make sure the name of your data disk appears as the destination where the information will be saved. If you click the Desktop button, you should see your disk name on the list. Double-click the name to oper your disk. If you can't find it, ask for assistance.Then click on Save.

将声音样本保存到您的磁盘上，并使用一个能明确标识它的名称——分析时将需要找到这个文件。要保存，请从文件菜单中选择'保存实验为...'。系统会提示您输入名称，但输入名称后必须确保数据磁盘的名称显示为保存位置。如果点击桌面按钮，您应该能在列表中看到磁盘名称。双击名称以操作该磁盘。如果找不到， please ask for assistance。然后点击保存。

5. Repeat the capture and disc save operations for your other two sounds. You may now take your disc and complete your analysis on any of the laboratory computers by using the Sound program on any of them.

5. 对你的其他两个声音重复捕获和保存操作。现在你可以使用其中任意一台实验室电脑上的Sound程序，完成对磁盘的分析。

6. Experiment with the display of your waveform until you have a clear display of at least one cycle of the waveform (preferrably about four cycles) , scaled so that it nearly fills the display vertically as well as horizontally.

在波形显示上进行实验，直到显示出至少一个周期的波形（最好是四个周期），并调整比例，使波形在垂直和水平方向上几乎填满显示区域。

7. With your waveform display on the screen , choose Analyze A from the Data menu to display a vertical line on the screen. Using the mouse, position that line on the first distinct peak of the waveform and note the time. Then move it to the right to cover as many full periods of the wave as possible and note the corresponding peak time. Calculate the period and then the frequency of the sound. When you have finished this analysis, click the "Done" button on the screen to take you back to the standard display.

7. 将波形显示开启在屏幕上，从数据菜单中选择'分析A'以在屏幕上显示一条垂直线。使用鼠标将该线定位在波形的第一个明显峰点上，并记录时间。然后将其向右移动，使其覆盖尽可能多的完整周期，并记录对应的峰时间。计算周期，然后计算声音的频率。完成此分析后，点击屏幕上的'完成'按钮以返回标准显示。

8. Click on the display of the wave with the mouse to select it and then choose Copy from the file menu to copy this display onto the "clipboard" of the computer. Find and open the wordprocessor (Word) by choosing its icon under the Apple menu (far left, top of screen). Then choose Paste from its file menu to paste in your waveform display. Then save this as a wordprocessor document. You will be adding to this file to compose your laboratory report. Note: make sure you don't use the same title for your report as for any of your data files - it will overwrite it. Be sure to save it on your laboratory disk (i.e., make sure the name of your data disk appears before clicking Save.) You will be adding to this file to compose your laboratory report.

8. 用鼠标点击波形显示区域以选择它，然后从文件菜单中选择'复制'，将此波形显示复制到计算机的'剪贴板'中。找到并打开文字处理器（Word），通过选择苹果菜单（屏幕左上角）下的图标来启动它。然后从文字处理器的文件菜单中选择'粘贴'，将您的波形显示粘贴进去。将此文件保存为一个文字处理器文档。您将在此文件中添加内容以撰写实验报告。注意：请确保您的报告标题与任何数据文件的标题不同，否则会覆盖原有文件。务必在保存时将文件保存到您的实验盘（即在点击保存前，确保文件名中包含您的数据盘名称）。您将在此文件中添加内容以撰写实验报告。

9. Type a description of the sound in your wordprocessor file along with the waveform you have saved there, including your measured dBA level, the time data you recorded for determining the period, and the calculated frequency of the sound above the display. Choose Save from the File menu each time you make changes to keep your report up-to-date.

在你的Word处理器文件中输入对声音的描述，包括你保存的波形图，以及你测量的dBA电平、用于确定周期的时间数据，以及显示上方计算出的声音频率。每次修改后，都要从文件菜单中选择‘保存’以保持报告的最新状态。

对你的其他两个声音重复这个过程。

11. Produce frequency analysis plots of each of your three signals by the following procedure:

通过以下步骤对你的三个信号分别生成频率分析图：

a. Display the wave in the graph window. Click with the mouse at one peak of the waveform and hold the mouse button down while you drag diagonally across the graph to draw a dashed rectangle which encloses exactly one period of the wave. The display will change to display the selected range. You may refine the process to fit more accurately to one period if necessary.

在图形窗口中显示波形。用鼠标点击波形的一个波峰，然后按住鼠标键拖动 diagonally 跨越图形，绘制一个虚线矩形，使其恰好包含一个周期的波形。显示会切换到所选区域。如果需要，可以进一步调整以更准确地匹配一个周期。

b. With two quick clicks of the mouse on the graph (called "double clicking"), you will display the window for choosing graph scales. Place the mouse pointer over the small rectangular window to the right of "Type of Graph" and you will receive an option to choose Data or FFT. Move the pointer to FFT and release the mouse button. Click OK at the bottom of the window plot of amplitude versus frequency will be displayed. This is your sound analysis. Click on it with the mouse and choose Copy from the Edit menu to copy it to the clipboard. Open your wordprocessor document and paste this analysis in below your waveform display of this same sound. This may be done by clicking the mouse below the waveform to establish an entry point and then choosing Paste from the Edit menu.

b. 用鼠标快速点击图形两次（称为"双击"），您将显示选择图形尺度的窗口。将鼠标指针移到"图形类型"右侧的小矩形窗口上，您将获得选择数据或FFT的选项。将指针移到FFT并释放鼠标按钮。在窗口底部点击确定，幅度与频率的图形将显示出来。这是您的声音分析。用鼠标点击该图形并从编辑菜单中选择"复制"，将其复制到剪贴板。打开您的文字处理器文档，在此声音的波形显示下方粘贴此分析。这可以通过在波形下方点击鼠标以确定入口点，然后从编辑菜单中选择"粘贴"来完成。

12. Compare your calculated frequencies in Hz with the Equal Tempered frequency chart and label the frequencies in your report with the nearest equal tempered note. The indented numbers are the sharps and flats.

将你计算出的频率（单位：Hz）与等音律频率表进行比较，并在报告中用最接近的等音律音符标注这些频率。缩进的数字表示升音和降音。

III. 使用 MacScope 接口进行声音分析

The MacScope interface offers a higher quality digitization of sound signals than the Universal Laboratory Interface used in the first part of this analysis laboratory series. The MacScope is to be used to digitize a sample from each of your three recorded sounds and to analyze the sound. The results are to be added to the wordprocessor file on your disk to complete your sound analysis report.

MacScope接口提供的声音信号数字化质量优于本分析实验室系列前一部分所使用的通用实验室接口。MacScope将用于对您所记录的三个声音中的每一个进行采样，并进行声音分析。分析结果需添加到您的磁盘上的字处理器文件中，以完成您的声音分析报告。

1. Play your tape and adjust the amplitude with the blue monitor control so that you get a waveform about 2 volts peak-to-peak (about 4 divisions peak-to-peak with the VOLTS/DIV set at 0.5).

播放磁带并使用蓝色监视器控制调节幅度，使波形约为2伏峰峰值（当VOLTS/DIV设置为0.5时，约为4格峰峰值）。

2. Replay the tape and when you see the waveform, use the mouse to click the STOP/GO button on the MacScope screen. There is a delay before data appears on the screen - once it appears on the screen, click the STOP/GO button again to stop collection. An asterisk will appear (Stopped*) which shows you that data transfer to the computer is still going on. Wait until it disappears to proceed.

重放磁带，当看到波形时，用鼠标点击MacScope屏幕上的STOP/GO按钮。数据出现在屏幕前有延迟——一旦数据出现在屏幕上，再次点击STOP/GO按钮以停止采集。会出现一个星号（Stopped*），这表明数据仍正在传输到计算机。等待星号消失后再继续。

3. SAVE THE FILE IMMEDIATELY! (The software is very crash-prone, and saving the file will allow you to reconstruct it.) To save, choose "Save MacScope File..." from the File menu, give it a title, click the Desktop button and direct the Save to your disk. Use a name which you will recognize and which does not duplicate anything on your disk.

立即保存文件！（该软件非常容易崩溃，保存文件将允许你重新构建它。）要保存，从文件菜单中选择“保存MacScope文件...”，给它一个标题，点击桌面按钮并将保存位置指向你的磁盘。使用一个你能够识别的名称，并确保该名称不与磁盘上的其他文件重复。

4. Use the slide bars and controls on the display to adjust it to almost full height of the screen and with at least two full periods showing in the window. The width of the waveform on the display is adjusted with the T slider at the top of the screen. The height is adjusted with the V slider to the right.

4. 使用屏幕上滑动条和控制按钮，将显示调整到几乎占屏幕全高，并确保在窗口中显示至少两个完整的周期。屏幕上顶部的T滑块用于调整波形的宽度，右侧的V滑块用于调整波形的高度。

5. Use the mouse to carefully enclose precisely one period in a rectangle, observing the data box which is displayed on the screen so that you can write down the frequency of the wave for your report. That portion of the curve will be highlighted. Then choose Fourier Analysis from the Analyze menu. The harmonic amplitudes will be displayed in a bar graph below the waveform. Click on the Expand button to expand the display for the widest bars in the bar graph. You may need to use the V slider to readjust the waveform so that it will all fit in the window.

5. 使用鼠标仔细地将一个周期围成矩形，观察屏幕上显示的数据框，以便可以将波的频率写入报告。曲线的这一部分将被高亮显示。然后从分析菜单中选择‘傅里叶分析’。谐波振幅将在波形下方以条形图形式显示。点击‘展开’按钮以展开条形图中宽度最大的条形。可能需要使用V滑块调整波形，使其全部显示在窗口内。

6. The display of the waveform and its analysis is to be made a part of your report. Move the mouse cursor off the display so that it doesn't show and then save an image of the screen by simultaneously holding down the Command and Shift keys and press 3 while those keys are still down. This will store a graphic image of the screen under the title screen0, screen1, or picture0, picture1, etc.

波形的显示及其分析应作为你的报告的一部分。将鼠标光标移出显示区域，使其不显示，然后通过同时按下Command和Shift键并按3键来保存屏幕图像。这将把屏幕的图形图像保存为名为screen0、screen1、picture0、picture1等的文件。

7. Before closing this data file write down the following data to include in your report:

在关闭此数据文件之前，请写下下列数据以包含在您的报告中：

a. The frequency you obtained from part 4 above. If you did not note it then, you can now redraw the rectangle over the same period and record that frequency.

你从上一部分得到的频率。如果你之前没有记录下来，现在可以重新画出同一周期的矩形并记录该频率。

b. Click on the FFT Data button to display the table of harmonic amplitudes. Write down just the harmonic number and the amplitude in the column next to it for all the harmonics which show amplitudes of .02 or more. Include a table of these amplitudes in your report with the graphical display saved above. (Alternatively, you can just take a picture of the data table and patch it into your report.

b. 点击FFT数据按钮以显示谐波振幅表。记录所有振幅大于或等于0.02的谐波的谐波次数及其对应的振幅。在报告中包含这个振幅表，并将上述图形显示保存起来。（或者，你可以直接拍摄数据表并将其插入到报告中。）

8. Close this data file and repeat the process for your other two sounds on the tape. To get back to the screen for collecting data as in Step 2, click the Scope button at the top of the display.

关闭这个数据文件，然后对磁带上其他两个声音重复上述过程。要回到如步骤2中收集数据的屏幕，点击显示顶部的Scope按钮。

9. You must now transfer the graphic screen image files titled screen_ or picture_ onto your data disk. By default, they are stored on the hard disk of the machine. Find them and copy them to your disk by dragging their icons to your disk icon on the side of the screen.

现在，您必须将名为screen_或picture_的图形屏幕图像文件转移到您的数据盘上。默认情况下，这些文件存储在机器的硬盘上。找到它们，并通过将图标拖到屏幕侧面的盘图标上，将其复制到您的盘中。

10. Open your lab report file with the wordprocessor. Also open the graphic program DeskPaint by selecting it from the Apple menu (far left). Use DeskPaint to open the first of your Screen_ or Picture_ files. Use the dashed rectangle tool to draw a rectangle around just the waveform display and the Fourier analysis below it. Choose Copy from the Edit menu to copy this image. Then choose the wordprocessor from the extreme right hand menu to bring up your report and paste this graphic into your report. Add the frequency and harmonic amplitude data by typing it in below the display. Repeat for the other two screen files so that you have all three waveforms and the accompanying data in your report.

打开你的实验报告文件，使用文字处理器。同时，通过选择苹果菜单（最左边）打开图形程序DeskPaint。使用DeskPaint打开你的Screen_或Picture_文件中的第一个文件。使用虚线矩形工具，在波形显示区域及其下方的傅里叶分析部分画一个矩形。选择编辑菜单中的“复制”命令，复制这个图像。然后选择右侧最末端的“文字处理器”选项，打开你的报告，将此图形粘贴到报告中。在显示区域下方输入频率和谐波振幅数据。对其他两个屏幕文件重复此过程，使你的报告中包含所有三个波形及其相应的数据。

Below is an example of the type of display that should be a part of your report:

以下是一个应包含在报告中的显示示例：

语音波形，元音“AH”，频率215 Hz

IV. 傅里叶分析与合成

You will be using a simple Fourier synthesizer which is able to produce up to nine harmonics with variable phase. A recorded sound from a short closed organ pipe will be provided as a test case for Fourier synthesis.

你将使用一个简单的傅里叶合成器，它可以生成最多九个谐波，并且具有可变的相位。一个短的封闭风管录制的声音将作为傅里叶合成的测试案例。

First analyze the sound of the organ pipe using the MacScope A/D converter. Using the analysis of one period of the sound, extract amplitudes and phases for the harmonics present in the sound. Although we don't hav a precise way to control phase, you are match the amplitudes of the harmonics with the Fourier synthesizer and make some attempt to adjust the phase so that the waveform looks like that of the tape of the pipe sound. Listen to the two sounds and comment on their similarity or differences.

首先使用MacScope A/D转换器分析管风琴管的声音。利用对一个周期声音的分析，提取出声音中各谐波的振幅和相位。虽然我们没有精确控制相位的方法，但你可以将各谐波的振幅与傅里叶合成器匹配，并尝试调整相位，使波形看起来像管风琴声音的磁带。听这两个声音，并评论它们的相似之处或差异。

Sound Analysis

Physics 4060, Acoustics Laboratory

Physics 4060 Laboratory