1/4 "自由场传声器，外部极化
专为在 4 Hz 至 100 kHz 频率范围内进行高声级和高频测量设计的自由场传声器。
4939 型
使用不锈钢振膜和保护格栅4939型传声器专为承受恶劣环境而设计，可用于高达150°C（302°F）的高温测量。
该传声器需要外部极化电压，因此必须与经典的前置放大器一起使用。外部极化传声器可以在较高温度下使用，而不会对测量灵敏度产生严重影响。
| Standard | IEC 61094 |
| Sound field | Free field |
| Polarization voltage | 200V |
| Sensitivity | 4 mV/Pa |
| Lower limiting frequency | 4 Hz |
| Higher limiting frequency | 100 kHz |
| Inherent noise | 28 dB(A) |
| Upper limiting of dynamic range | 164 dB |
| Diameter | 1/4 inch |
| Venting | Side |
| Minimum Temperature | -40 °C |
| Maximum Temperature | 150 °C |
| Minimum Temperature | -40 °F |
| Maximum Temperature | 302 °F |
A laser-welded, stainless-steel diaphragm ensures superior long-term stability and mechanical robustness. Type 4939 will withstand the 1 m drop test required by IEC 60068-2-32.
The microphone is assembled in a clean room, ensuring that the microphones maintain their inherent noise floor and high stability, even when used in environments with a combination of high humidity and high temperature.
Type 4939 is available in a TEDS Microphone set with different variants of classical preamplifiers. The TEDS microphone is considered one unit and has been sealed in a clean environment.
The TEDS is programmed with the loaded sensitivity of the actual cartridge and the data is therefore readily available in the transducer. The default TEDS template is according to IEEE P1451.4 but TEDS to IEEE 1451.4 is available on request.
The sensitivity can be calibrated at 250 Hz by using Pistonphone Type 4228 with ¼-inch Adaptor DP 0775. The actuator response can be measured using Actuator UA 0033 with Adaptor DB 0264.
The free-field response can be obtained by adding the type-specific, free-field correction to the actuator response.
This will bring together HBM, Brüel & Kjær, nCode, ReliaSoft, and Discom brands, helping you innovate faster for a cleaner, healthier, and more productive world.
This will bring together HBM, Brüel & Kjær, nCode, ReliaSoft, and Discom brands, helping you innovate faster for a cleaner, healthier, and more productive world.
This will bring together HBM, Brüel & Kjær, nCode, ReliaSoft, and Discom brands, helping you innovate faster for a cleaner, healthier, and more productive world.