直接场声学测试系统
高强度声学测试（HIAT / High Intensity Acoustic Testing）的目的是在实验室中以可控的方式再现有效载荷在发射时将承受的强烈声场，以验证设计是否能够承受这种声场，从而安全地完成其轨道之旅。如今，主要有两种方法实现高强度声学测试，即混响声音测试设施（RATF / Reverberant Acoustic Test Facility）和直接场噪声测试（DFAN / Direct Field Acoustic Noise Testing）（备注：DFAT [Direct Field Acoustic Testing / 直接场声学测试] 已经被其他公司注册为商标，下文中使用非商标缩写DFAN表示DFAT）
由于DFAN相对RATF而言，具有便携性、较低的建造和维护成本等特点，以及对声场的频谱和空间细节有更严格的控制能力，使得DFAN的应用越来越广泛。
图1 直接场声学测试相关指南与规范
MIMO DIRECT FIELD ACOUSTIC CONTROL 直接场声学测试MIMO控制系统
Data Physics公司的MIMO直接场声学测试控制器为声学噪声测试提供扬声器控制。800系列MIMO声学控制器可以产生均匀的声场。
图2 DFAN测试的扬声器阵列
图3 SPL控制水平和公差带
图4 声场均匀性
直接场声学测试是混响场声学测试（RATF）的一种替代方法。DFAN测试是根据NASA-HDBK-7010的指导进行的。
与RATF相比，DFAN在降低产生声场所需的设备成本以及减少设施/基建成本方面具有一定的优势。
Data Physics公司的直接声场控制器采用了为其多振动器振动控制器开发的多输入多输出（MIMO）控制技术，以达到所需的声压级，同时确保声场均匀。
系统组成
Data Physics公司的直接场声学测试系统主要由Data Physics Matrix™ Controller、（用于麦克风阵列测试测量）Data Physics DP906 DAQ、扬声器阵列、监控麦克风等组成。
800系列声学控制器 |
Matrix™ Controller |
DP906 DAQ |
扬声器阵列 |
麦克风阵列 |
SignalStar Matrix Random Acoustic Control技术参数
Control Parameters | |
Profile Type: | 1/1 octave, 1/3 octave, narrowband |
Frequency Range: | Selectable from 37 ranges, 20 Hz to 20 kHz. |
Narrowband Resolution: | 25, 50, 100, 200, 400, 800, 1600, 3200, and 6400 lines. |
Input Channels | |
Number: | 4 to 32 |
Types: | Control, Measurement |
Engineering Units: | Table of over 50 engineering units, plus user specified units, time and frequency domain integration is done by selecting unit in graph attributes, includes unit conversion and offset removal |
Reference Profile | |
Definition: | 1/1 octave, 1/3 octave, narrowband |
Breakpoints:. | Defined as level or slope |
Alarm and Abort: | Limits defined in dB or % relative to reference profile. |
Run Schedule |
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Definition: | Test may consist of an unlimited number of test stages |
Stage Parameters: | Level (dB), Duration (hhh:mm:ss), Control averaging parameters Enable or disable measurements, data save, and abort |
Manual Operations During Test | |
Test Execution: | Start, Stop, Resume test |
Stage Control | Move between stages or hold at current stage. |
Correction Rate | Modify correction rate |
Control Loop | Open or closed |
Alarms & Aborts | Enable or disable |
Modify Refeence: | Modify level in individual 1/1 or 1/3 octave reference bands |
Save Data |
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Safety | |
Safety Checks: | Continuous measurement and detection of safety limits |
Open microphone: | Open loop detection and abort |
RMS Limits | High and low limits for alarm and abort specified in dB or % |
Spectral Limits: | High and low limits for alarm and abort specified in dB or %, user-defined number of spectral lines to exceed limit |
Shutdown: | User defined shut down rate in seconds. |
Drive Limit: | Drive output voltage limiting |
Throughput to Disk (optional) | |
The Throughput to Disk option provides continuous throughput of time histories to local ABACUS throughput disk at up to 100 kHz sample rate on all channels during test | |
Signals for Display and Save | |
Control | Control, Reference, Alarm +/-, Abort +/-, Drive |
Limit | Alarm, Abort, Profiles |
Measurements (all active channels) | Time, Narrowband Spectrum, 1/1 octave, 1/3 octave |
Test Status Displays | |
Status Displays: | Elapsed and Remaining Time, Reference Level, Control Level, System Status Messages, Channel status |
All specifications subject to change without notice.