基于声卡的虚拟信号发生器的设计外文翻译

. . . . 师大学本科毕业设计(论文)外文翻译译文：软件为计量大的特征性PC声卡Jan Saliga和Linus Michaeli1电子通讯系，高冰大学摘要：论证了一种虚拟仪器软件，使得简单而快速的性能测试和计量特征的任何PC机在波形记录的应用。除了在时间和谱域对记录信号模式的观察，软件直接计算各种各样输入模拟通道的基本计量参数，例如，根据1057和1241和 DYNAD的IEEE标准：有效位的数量，总谐波失真，总谐波失真加噪声，信噪比等。在确定模型参数进行的时间以与在光谱领域比较所取得的结果。在软件开发LabWindows/CVI（C语言）和实行的低层次的Win32API多媒体功能。作者的意图是应用软件进行计算机部件供应商,为教育示的ADC测试原理文章还包括了几个例子，取得了有趣的结果从测试一些PC声卡和实用的作者的经验，从个人电脑声卡的测试。关键词：PC声卡；波形记录仪测试；ADC的动态测试；虚拟仪器软件文章大纲1. 介绍2. 动态测试方法进行波形记录仪基于插板3. 声卡为波形记录仪4. 测试软件和安装特点5. 实例测试结果的实现6. 结论参考1.介绍声卡,有时也被称为“录音机”，同时录音机经常被用于许多计算机(PC)的功能。它们可以被认为是他们的“标准”音频(模拟)接口。通常声卡比多功能机机和工业数据采集插板便宜10到100倍。另一方面，模拟输入和输出参数宣布由供应商，如至少16位模拟至数字和数字到模拟转换器（ADC和DAC），决议的可能性表示这样的声卡生成低成本，低频率的数据采集系统，可以从化学，压力，振动等传感器的信号。建立了完善的声卡的频率带宽可以延长直流或半直流信号通过应用菜刀，或者由在PC卡输入数字调制解调其次放大器。这些思想，以与在同行业中的挑战，促使作者进行模拟信号录音通道一些测试根据IEEE标准1057和1241和DYNAD草稿中的实例验证声卡的应用可能性表示的大不一样过。新的专有虚拟仪器（VI）软件开发，必须进行实验和测试。2动态测试方法进行波形记录仪基于插板标准的测试方法进行波形记录仪通常是众所周知的，他们也带出一个全面的形式IEEE性病。10571。目前，新的，即将被公认标准IEEE性病。12412，3DYNAD来与一些新的理念和测试步骤进行更详细的讨论。此外，很多研究者已经提出了许多观点和方法来解决 AD 和 DA 的转换测试问题，对于那些观点的信息反馈和调查正在广泛地进行4 。经过比较各种标准，得知IEEE标准1057数字化波形录音器标准是与声卡测试最接近的一个。然而，这个标准涵盖了静态和准静态测试大多主要基于直方图方法测试，其不足的程序和数据处理方法，确定细节测试ADC的动态参数,特别在频域。基于直方图方法的一般都是非常方便的，因为声卡的特征性交流耦合对信号输入的卡片(图1)。图1 .典型的功能框图的模拟信号和数字电路的信号记录仪的一部分在音效卡标准都更关注行动一致并且独立的可测试,但他们包含了很多的细节上执行和评价的一些动态测试。特别是DYNAD草案中蕴涵着极其详细描述数据的处理，对评估过程中参数ADC的动态光谱域。这些事实，以与有很多相似之处，也和数字化测试波形记录仪、导致申请的决定，很多程序详见DYNAD IEEE性病的评估。1241 ADC的动态参数对计算机声卡测试波形记录仪中扮演的角色。测试波形记录仪在PC插件板的形式有一些细节。PC的部通常是准确的数字私密的某一输入信号。提出了开发和测试方法以与一些实现多功能工业试验均为在各种各样的情形下插板,已发表在5,第6和第7条。作者们更喜欢动态测试方法基于FFT频谱或正弦曲线拟合和确定有效的比特数(第三)和测试频率为主要质量的特征性参数的测试板。在软件领域,两个通用版本的VI测试软件已经发展和出版在LabVIEW9和另外的Matlab8。两个版本的软件已经很普遍assignations-they过程数据从任何测量记录在一个文件时,他们不包含任何数据采集部分。3声卡为波形记录仪一般都是致力于声卡录音和玩声音信号。这一结果在限制的输入与输出频率,通常用来频率跨度带宽从20赫兹到20千赫，避免应用静态测试方法的应用,导致的动态检测方法采用正弦输入测试信号。典型的功能框图的声音拼输入记录通道图1显示的是(10-11和其他的)。模数转换积分的转换器转换通常雇工作的modes-8在至少两个精度和16位。 数据能被编码成几个非线性和线性格式。线性格式(PCM)，这是最适合的格式的性能测试,他被选中在发达的测试程序。各种各样的可选的采样频率取决于声卡model-at至少8、11、16和44.1 kHz-are通常所提供的。稳定性,而且最终,多普勒频移的这些频率通常不被明确地表明在音效卡的使用手册。Digitising输入就可以转移的一场模拟多工器。麦克风输入和一个较不敏感的线录和麦克风(辅助)输入是置在为连接外部模拟信号的来源。音效卡在可能是最经常使用的个人电脑与操作系统(OS)Windows 9x / NT / 2000 /我/ XP。任何声音应用在Windows下可以使用一些三个层次的Win32 API多媒体课件的职能,为控制和数据转移/从任何Windows兼容的声卡。MCIWnd最高的窗口类，MCI设备中间接口，低层音频接口，应用程序使用的最好的可能，需要控制的音频设备。4测试软件和安装特点一般安装所需要的声音录音部分射性能测试是非常简单的(图2)。它是由一个精确的测试信号发生器和普通PC机和音效卡计算机机箱的考验。DS360超低失真的发电机，斯坦福研究系统与20位DAC和拉力比100分贝是用于测试的设置。测试的音效卡(ATX)和各种各样的新老(在)计算机机箱不同万块主板和在一些笔记本。图2 设定了声卡的测试此安装必须结合一个方便的软件,它必须控制声音激射测试，收集和处理的记录的数据，以与目前和档案的结果。当前通用软件8-9不包含任何部分的资料收集，他们可以使只有数据处理。一个可能的附加变形记录的数据，这可能是由于使用第三方软件，未知数据获取详细记录从一个语音卡在一个非线性的格式，导致这个决定开发一种新的特殊VI的软件。该软件被创造的目的是最大的综合性在音效卡的测试。它是完全结合其低层数据录入子程序，它可以作为一个可执行文件安装在任何PC视窗操作系统和正确安装声卡包括安装的Windows兼容的司机。软件开发环境LabWindows /约定保险价值的民族乐器的支持下，软件开发工具包(SDK由微软)，被用来作为主要的software-developing工具。用户面板被显示在图3。图3 用户VI前面板的开发软件这种软件能够使：记录数据从任何声音卡在标准8/16位和单色和立体声模式在一个可选的标准的采样频率，在线性PCM格式。用户可以跟上录音过程和简单地识别任何问题从文本信息中显示的窗口。观想记录的数据，包括为视觉评价,嗡嗡作响,也用来储存和阅读记录的数据/从一个文件。在分析记录数据时域：选择性地的四性能均配件和噪声功率,有效的枚举第三位的数字和其他派生的参数。真正的采样频率估计的0.9%。价值的估计DC测试信号的幅值和相位。分析和可视化的记录的数据在光谱域：计算功率密度谱和功率谱分布函数。估计基本的谐波，总谐波失真，总谐波失真加噪声，信噪比第三和其它参数计算出的功率密度谱。根据接收到的迭代算弦波拟合有点改变，以IEEE标准,因为它的收敛问题。在应用算法始于计算正弦适合和相应的噪声功率PN0频率fn0立足fsamplingsf = fsignal /()高于其估计和fsampling由给定的fsignal通过采样频率偏移三藩市 1。接下来的两个组合和相应的噪声，PN2权力(PN1在频率计算fnk)/(fsamplingsf = fsignal + kfstep)(k = 0、1、2)，在那里fstep0步骤是开始的采样频率为最小的PN搜索程序。PNk值比较，无论是fn0降低或fstep在下一次迭代。迭代过程中之间的区别是停止PNk低于武装的限制。当然，如果迭代过程中收敛的fsignal评估和fsampling是相当的接近他们确切的价值观和三藩市选用适当。5。实例测试结果的实现到目前为止，8个型号的音效卡进行试验研究。它们可以被分为两组：PC声卡上实现主板或在笔记本上。“插件”独立声卡。第一个测试模型集成在相对较新的声音blasters m805lr ATX主板和m807r用PC芯片1213于2000年。Socket-462主板支持的低功耗总线(Socket-A)处理器的速度200或266兆赫。 他们用这些通过VT8363芯片组,它提供了一个4 AGP插槽高度的图形显示、中央处理器的即插即用通过固件。主板所建的在同一AC97音频编解码器,提供了现代隔水管(AMR)槽来支持音频和现代的应用程序。有一个建的m805lr 10BaseT / 100BaseTX。 卖方指定执行AC97具有如下特点:“支持18-bit解码器ADC和DAC,以与18-bit立体声全双工编解码器”12和13。这两个样本,个人计算机芯片和一个m807r m805lr,进行试验研究。一些结果在一个取样频率的44.1千赫是列在表1和表2以与在图4和图5。表1 测试结果，从第三编解码器上实现声音的形式m805lr PC芯片主板:结果拟合/结果频谱全尺寸表( 1K)表2.测试结果,从第三编解码器上实现的声音l807r主板PC芯片全尺寸表( 1K)图4 (a)第三依赖测试信号频率的8和16(*)-()-bit单声道模式m805lr编解码器在PC上芯片的声音。(b) 典型的谱在16位模式在PCCHIPS m805lr声音编码器(测试频率是2.1千赫)。图5 (a)第三依赖测试信号频率的8和16(*)-()-bit单声道模式m807r编解码器在PC上芯片的声音。(b)典型的16位模式谱在PCCHIPS m807r声音编码器(测试频率是认识千赫)。所取得的结果表明价格之间的差距太大了供应商的宣布参数和真正的问题。特别是在16位模式，最大限度地达到第三价值总是降到10位元m805lr和略多于10位元m807r。此外，依赖急剧减少的第三输入测试信号的频率在大约5千赫兹的频率在m805lr被分配。同时，a / d转换器输入围的偏移量。28846进入midpoint-112代替128,进入32768-was检测。 它会减低输入电压围。最后要说明的是更好的价值观为m807r参数,取得了。它是相当奇怪的,因为它们都主板使用一样的声音晶片。光谱比较,如图4和图5的广告nonharmonics低得多的m807r扭曲的。改变采样频率并没有导致任何改变都克服0.1-bit l80x板。进一步的测试声音的CM8330射来的正是建立在芯片14集成在主板m559在老用PC芯片。第一次试验,结果表明一个非常低素质的声音并导致射来的录音机部分取消任何下一步的测试。这个原因可以看出在图的局限性。6-the地板在水平测试信号进入62 16000多人,减低了所有的测试质量参数的录音机厘米,防止声音晶片8330射来的正确的决定的其他录音机参数。图6 记录正弦波为16位模式由m55 水平上的限制16,062完全降解CM8330参数在笔记本上的音效卡，实现进行了测试。最有趣的结果，取得了TravelMate在笔记本212TX16，宏碁与音频16位AC 97年立体声编解码器。表3和图7说明其中的一些。表3 结果从第三编解码器实施测试的声音212TX宏碁TravelMate笔记本全尺寸表( 1K)图7 .(a)第三测试信号频率的依赖(*)的8 - 16单声道模式(声音的)-bit宏碁实现TravelMate射来的212TX笔记本。(b)典型的16位模式谱，宏碁实现声音TravelMate射来的笔记本212TX(测试频率采样频率44100 4.11千赫,赫兹)。(c)详细的典型谱的16位模式实施的声音在笔记本宏碁TravelMate射来的212TX 11.11(测试频率采样频率44100赫兹)。所取得的结果提示,同样在此之前，一个糟糕的音频输入的质量检测笔记本特别是在16位模式。此外，那奇怪的频谱如图。7b和c意味着一个想法，即真正的采样频率的声音编解码器是不同于设一或者数字滤波的积分模数转换器不正确的工作。最后一个例子是“独立的”插件板声激射PCI6415通过创造性的技术。一些实现的结果显示在表4和图8和图9。在与过去相比,此牌blasters证明声音轻轻更好的计量参数。表4。第三依赖测试信号频率的声音PCI64射来的图8。(a)第三测试信号频率的依赖(*)的8 - 16单声道模式(声音的)-bit射来的一种总线标准64。(b)典型的谱在16位模式(测试频率声音拼PCI64 211赫兹，采样频率44100赫兹)。图9。观察到的声音失真为输入信号PCI64会议射来的全尺寸的音频输入(输入频率21赫兹，采样频率44100赫兹)。声卡的8位模式似乎非常接近理想的结果就缺超过8位是造成真正的量子化的比较理想的噪声信号和归一化的力量是简化，在大多数的标准是1 / 12。然而，最大限度地实现价值是在16位模式第三只略微超过12位,这仍然是远离宣布16位分辨率。而且,如果输入信号满足几乎全尺寸的测试，明显的音频输入非线性失真的观察记录的数据(见图9)。测试一样的牌在不同的机器带来的只有微不足道的差异超过0.5点达到results-not。通常情况下，只有大约0.1一点。这个事实表明主要影响的计量参数语音卡有卡图案，不干扰其他的个人计算机的部件。6。结论开发的软件应用的测试和评价中几个声卡。这似乎是一种非常有用的tool-it使测量和习得的音效卡，许多复杂的参数在较短的时间。开发的软件就业用PC零售商可以导致质量的提高和信心的PC组件提供。本软件也将被用来在教育教学过程中，电子测量和数据采集系统在柯增强的冰科技大学作为一个示虚拟仪器的讲解和演示的标准ADC测试方法。不同声卡的测试结果都表明了从测量的角度上看音质较差。在16位模式下尤其明显。独立插入式声卡似乎比主板集成显卡好一些(好一两个字节)。电脑部零件似乎比声卡设计本身对于测量参数的干扰要小。种种事实都表明声卡只能用在不超过10到12个字节的简单的系统上。此外，不同声卡的测量参数存在着相当大的差异。参考文献：1 IEEE标准.1057-1994性病,数字化波形记录.2 IEEE性病,草案.1241覆盖.VS022500.3 DYNAD覆盖,草案,.fe.up.pt/.3.3 hsm / DYNAD,2001年.4 p . Arpaia Daponte .和p . Cennamo converters-a计量的特征性的模拟/数字,国家的艺术。论文的第三届国际会议上发表的A / D转换和先进D / A转换技术与其应用(09/10/1997.Publ.没有466章)(1999),页.134-144。 全文通过CrossRef帕斯| |观点被记录在斯高帕斯(0).5 m . Pokorny,第五卷,j . Roztocil、抑Haasz由AD-modules测试信号失真。 在:动态测试,IMEKO研讨会论文集,ISSDMI TC-4 98年的今天,意大利那不勒斯队(1998),页.889-892.6 m . Pokorny,第五卷,Haasz替代方法的A / D转换质量检测。在:Instrumentaion和测量技术研讨会,99论文集中的第16卷IEEE,意大利的威尼斯.3(1999): 1421-1424.全文通过CrossRef帕斯| |观点被记录在斯高帕斯(1)7 r . Holcer,性能测试的一些广告转换器中嵌入了微控制器。论文IMEKO世界大会的十六,IMEKO 2000年,诉讼,维也纳,奥地利(2000年):165-169。8 一、Kollar马库斯,正弦波的ADC的手段测试国际比较。在IMEKO:十六,IMEKO 2000年世界大会,诉讼,维也纳,奥地利(2000).9 j .布莱尔,Sine-fitting IEEE标准和软件为1241 1057年.论文的第16次IEEE仪器和测试技术研讨会,页。/ 99中的3(1999): 1504-1506.全文通过CrossRef帕斯| |观点被记录在斯高帕斯(14)10 模拟设备:广告1845年16位SoundPort平行端口立体声编解码器、产品应用手册,模拟设备,1997年.11 OPTi:82C931Plug和演奏声音控制器、产品应用手册,OPTi,1997年。12 电脑芯片:805lr用户手册.13 电脑芯片:807用户手册.14 电脑芯片m569用户手册.15 (.creativehelp./specs/audio/pci/es1370.html).16 (.acer.).原文：Software for metrological characterisation of PC sound cardsJn aliga ,and Linus Michaeli1Author vitae Department of Electronics and Telecommunications, Technical University of Ko ice, Park Komenskho 13, SK-04120, Ko ice, Slovak Republic,Available online 17 September 2002.Abstract：The paper demonstrates a virtual instrument software that enables the performance of simple and fast testing and metrological characterisation of any PC sound card in waveform recorder applications. In addition to the visualisation of recorded signal patterns in time and spectral domains, the software directly computes a variety of basic metrological parameters of input analogue channels, e.g. effective number of bits, THD, THD+noise, SINAD, etc., according to IEEE Standards 1057 and 1241 and DYNAD. The parameter determination is performed in time, as well as in spectral, domain to compare the achieved results. The software was developed in LabWindows/CVI (C language) with implementation of low-level Win32 API multimedia functions. The authors intention is to apply the software for computer component vendors and for the educational demonstration of ADC testing principles.The paper also contains a few examples of achieved interesting results from testing some PC sound cards and practical authors experiences from PC sound card testing.Author Keywords: PC sound card; Waveform recorder test; ADC dynamic test; Virtual instrumentation softwareArticle Outline1. Introduction2. Dynamic test methods for waveform recorders based on plug-in boards3. Sound card as a waveform recorder4. Test software and setup characteristics5. Examples of achieved test results6. ConclusionsReferences1. IntroductionSound cards, sometimes called sound blasters, are very common and are often used as components of many computers (PC) nowadays. They can be considered as their “standard” audio (analogue) interface. Sound cards are much cheaper than multifunction and industrial data acquisition plug-in boardsusually more than 10100 times.On the other hand, the parameters of analogue inputs and outputs declared by vendors, e.g. at least 16-bit resolution of analogue-to-digital and digital-to-analogue converters (ADCs and DACs), indicate the possibility to apply such a card in low cost and low-frequency data-acquisition systems acquiring signals from chemical, pressure, vibration and other sensors. The frequency bandwidth of a sound card can be extended on DC or quasi-DC signals by applying a chopper or a modulation amplifier on card input followed by a digital demodulation in the PC. These ideas, as well as the challenge in the industry, led the authors to perform some tests of analogue signal recording channels according to IEEE Standards 1057 and 1241 and DYNAD drafts to verify the application possibilities of sound cards in the examples indicated herein before. New proprietary virtual instrument (VI) software had to be developed to perform the experiments and tests.2. Dynamic test methods for waveform recorders based on plug-in boardsThe standard test methods for waveform recorders are generally well known, and they were brought out in a comprehensive form in IEEE Std. 1057 1. Nowadays, the new, about to be accepted standards IEEE Std. 1241 2 and DYNAD 3 are coming with some new ideas and test procedures described in more detail. Moreover, many researchers have contributed with lots of ideas and approaches to solve AD and DA converter test problems. Probably the widest survey of those ideas was made in 4.Comparing the standards, IEEE Std. 1057“Standard for digitising waveform recorders”is the closest to the task of sound card testing. However, this standard covers mostly the static and quasi-static tests methods based mainly on the histogram testing and there is a deficiency of procedure and data processing details on testing and determining the dynamic parameters of ADC especially in the frequency domain. The histogram-based methods are generally not very convenient for sound card characterisation because of the AC coupling on signal input of the cards (Fig. 1).Full-size image (9K)Fig. 1. Typical function block diagram of analogue and digital circuits for signal recorder part in sound cards.View Within ArticleBoth on-coming standards are more focused on testing stand-alone ADCs but they contain much more specific details on execution and evaluation of some dynamic tests. Particularly, the DYNAD draft contains very detailed descriptions of data processing for estimation of the ADC dynamic parameters in the spectral domain. These facts, as well as many similarities in testing ADCs and digitising waveform recorders, led to the decision to apply many procedures referred in DYNAD and in IEEE Std. 1241 for evaluation of ADC dynamic parameters on PC sound card testing in the role of waveform recorder.Testing waveform recorders in the form of PC plug-in boards have some specifics. The interior of PC is generally illicit for a precise digitalisation of an input signal. The test methods developed and suggested, as well as some achieved test results for multifunction industrial plug-in boards in various circumstances, have been published in 5, 6 and 7. The authors preferred the dynamic test methods based on FFT spectrum or sinusoidal curve fit with determining effective number of bits (ENOB) versus test frequency as the main quality characterisation parameter of the tested board.In the software area, two universal versions of VI test software have been developed and publishedone in LabVIEW 9 and another in Matlab 8. Both versions of software have very general assignationsthey process data from any measurement recorded in a file and they do not contain any data acquisition part.3. Sound card as a waveform recorderSound cards are generally dedicated to recording and playing sound signals. This results in a restriction of input and output frequencies span, usually to the frequency bandwidth from 20 Hz to 20 kHz, which prevents application of the static test methods and leads to the application of the dynamic test methods using the sinusoidal input test signal. The typical function block diagram of sound blaster input recording channels is shown in Fig. 1 ( 10 and 11 and others).The analogue-to-digital conversion usually employs sigmadelta converters that can work in at least two precision modes8 and 16 bits. Data can be coded into a few nonlinear and linear formats. The linear format (PCM), which is the most suitable format for the performance test, was chosen in the developed testing procedure. A variety of optional sampling frequencies depending on the sound card modelat least 8, 11, 22.05 and 44.1 kHzare commonly offered. The stability and, eventually, a frequency shift of these frequencies are not usually explicitly indicated in sound card manuals. Digitising input may be switched by an analogue multiplexer. A microphone input and a less sensitive line-in (aux) input are built-in for linking external analogue signal sources.Sound cards are probably most often used in PCs with operational systems (OS) Windows 9x/NT/2000/ME/XP. Any sound application under Windows can use some of the three levels of Win32 API multimedia class of functions for controlling and data transferring to/from any Windows-compatible sound card: the highest MCIWnd window class, the middle MCI device-independent interface, the low-level audio interface, which is used by applications that need the finest possible control over audio devices.4. Test software and setup characteristicsThe general setup needed for performance testing sound blaster recording part is very simple (Fig. 2). It consists only of a precise test signal generator and a common PC with the sound card to be tested in a PC chassis. The ultra low distortion generator DS360 by Stanford Research Systems with 20 bits DAC and THD better than 100 dB was used in the testing setup. The sound cards were tested in various new (ATX) and old (AT) PC chassis with different motherboards and in a few notebooks.Full-size image (3K)Fig. 2. Setup for sound card testing.View Within ArticleThis setup must be integrated with a convenient software, which must control the sound blaster to be tested, collect and process the recorded data, as well as present and archive the results. The current general-purpose software 8 and 9 does not contain any part of data collecting and they enable only data processing. A possible additional distortion in the recorded data, which can be caused by using a third-party, unknown in detail recording software acquiring data from a sound card in a nonlinear format, led to the decision to develop a new special VI software.The software was created with the intention of maximal comprehensiveness at sound card testing. It was fully integrated with its low-level data recording subroutines and it can be installed as an executable file in any PC with Windows OS and correctly installed sound card including installation of its Windows-compatible driver. Software development environment LabWindows/CVI by National Instruments, with the support of the Software Development Kit (SDK by Microsoft), was used as the main software-developing tool. The user panel is shown in Fig. 3.Full-size image (49K)Fig. 3. User front panel of the developed VI software.View Within ArticleThe software enables: Recording data from any sound card in standard 8/16 bits and mono/stereo modes at an optional standard sampling frequency in linear PCM format. The user can follow the recording process and simply identify any problem from text messages shown in the message window. Visualisation of recorded data, including zooming for visual assessment, as well as saving and reading recorded data to/from a file. Analysis of recorded data in time domain: Performance optionally of four- and three-parameter fittings with enumeration of noise power, effective numbers of bits (ENOB) and other derived parameters. Estimation of real sampling frequency. Estimation of DC value, amplitude and phase of test signal. Analysis and visualisation of recorded data in spectral domain: Computation of power density spectrum and power spectrum distribution function. Estimation of basic harmonic, THD, THD+noise, ENOB and other parameters calculated from the power density spectrum.The iteration algorithm for the four-parameter sine wave fitting was a bit changed to IEEE standards because of its convergence problem. The applied algorithm starts with computing the sine wave fit and the corresponding noise power PN0 with the normalized frequency fn0=fsignal/(fsamplingsf) higher than its estimation from the given fsignal and fsampling by sampling frequency shift sf1. The next two fits and corresponding noise powers (PN1, PN2) are computed at frequencies fnk=fsignal/(fsamplingsf+kfstep) (k=0, 1, 2), where fstep0 is a beginning sampling frequency step for minimal PN searching procedure. Comparing PNk values, either the fn0 or fstep is decreased for the next iteration. The iteration process is stopped if the difference between PNk is lower than the armed limit. The iteration process converges certainly if the estimations of fsignal and fsampling are relatively close to their exact values and sf is chosen properly.5. Examples of achieved test resultsBy now, eight models of sound cards were tested. They can be divided into two groups: Sound cards implemented on PC mainboards or in notebooks. “Stand-alone” plug-in sound cards.The first tested models were sound blasters integrated on relatively new ATX mainboards m805lr and m807r by PC CHIPS 12 and 13 in 2000. The mainboards support Socket-462 (Socket-A) processor front-side bus speeds of 200 or 266 MHz. They use the VIA VT8363 chipset, which provides a 4X AGP slot for highly graphic display, CPU Plug and Play through firmware. The mainboards have built in the same AC97 Codec, providing an audio modem riser (AMR) slot to support audio and modem application. The m805lr has a built-in 10BaseT/100BaseTX. The vendor specifies following features of implemented AC97 Codec: “Supports 18-bit ADC and DAC, as well as 18-bit stereo full-duplex codec” 12 and 13. Two samples, the PC CHIPS m805lr and one m807r, were tested. Some results obtained at a sampling frequency of 44.1 kHz are presented in Table 1 and Table 2, as well as in Fig. 4 and Fig. 5.Table 1. Results from ENOB testing of sound CODEC implemented on mainboard PC CHIPS m805lr in form: results from fitting/results from