I. Overview
The MegaSig CM 311+A 803 is a measurement kit that includes a CM 311 pressure field ear simulator and an A 803 preamplifier. This type of artificial ear (Ear Simulator/Artificial Ear) has a long history, and its status in the electroacoustic engineering field is based on a very important international standard: IEC 60318-4 .
[Engineering History and Status] In 1981, the International Electrotechnical Commission (IEC) published the IEC 60711 standard, which defined the specifications for simulators that simulate the acoustic transmission impedance of the posterior half of the human ear canal (from the front of the earmold to the eardrum). This standard was later renumbered as IEC 60318-4, but experienced acoustic engineers still commonly refer to it as the ” IEC 711 artificial ear ” or ” 711 Coupler “.
The CM 311 is designed to physically and accurately reproduce the acoustic load defined by this standard. It simulates the acoustic characteristics of the human ear in an “occluded” state and is currently the globally recognized standard for measuring the frequency response of in-ear headphones and hearing aids . Data not verified by such equipment lacks credibility in the international market.
II. Core Functions and Technological Advantages of the Product
The CM 311+A 803 combines classic acoustic cavity design with modern electronic measurement technology. Its main technical highlights are as follows:
1. Acoustic characteristics conforming to international standards
- Standards compliance: Fully compliant with IEC 60318-4:2010 Ed.1.0 and ITU-T P.57 Type 2 artificial ear specifications. This means that data obtained using it can be directly compared with equivalent devices from major international manufacturers such as B&K or GRAS.
- Frequency response accuracy: Within the core human hearing range of 20Hz to 10kHz , the frequency response error is controlled within ±0.5dB ; in the high-frequency range of 10kHz to 16kHz , the error is controlled within ±1dB . This ensures a high degree of repeatability of the measurement curves.
2. Electrical specifications optimized for production lines and R&D
- High SPL withstand capability: The dynamic range of measurement covers 33 dBA to 143 dBSPL (THD < 3%). The upper limit of up to 143 dB makes it easy to handle distortion testing (THD measurement) of high-power headphones with minimal clipping.
- Standard sensitivity: The design sensitivity is 12.5 mV/Pa (-38 dB re 1V/Pa), which is the value recommended by the IEC standard, facilitating calibration and matching with various audio analyzers.
- Pre-polarized design: Paired with the A803 preamplifier, it uses IEPE (CCP) power supply mode, eliminating the need for traditional expensive 200V polarized power supplies. It can be connected to MegaSig PM series analyzers or other acquisition cards using a universal BNC interface.
3. Industrial-grade durability
- Material and structure: The main body is made of sturdy stainless steel, which is not only corrosion resistant, but also ensures that the acoustic cavity size remains stable at the micron level during long-term use.
- Environmental adaptability: It has a wide operating temperature range of -20℃ to 60℃ and can work stably at 10-90% relative humidity, making it very suitable for complex factory production line environments.
III. Usage Scenarios
The CM 311+A 803 is designed specifically for “sealed” or “insert” acoustic products, primarily for applications including:
- In-ear monitors (TWS) production line testing: This is the primary testing ground. By directly inserting or coupling the earphone nozzle to the opening of the CM 311, the actual frequency response of the earphones when worn in the human ear is simulated. Its high precision allows for the elimination of defective products with imbalances between the left and right ears or abnormal frequency responses.
- Hearing Aids Research and Calibration: Compliant with IEC 60318-4 standard, making it the standard basis for measuring various acoustic indicators of hearing aids (such as OSPL90, full-range gain, etc.).
- Active Noise Cancellation (ANC) Headphone Development: When developing ANC algorithms, it is necessary to accurately measure the relationship between the error microphone in the ear canal and the actual sound pressure at the eardrum (Transfer Function). The CM 311 provides a stable physical reference.
IV. Specifications
| Standard | ITU – TP .57, Type 2 sensor, IEC 60318 – 4:2010 Ed.1.0 |
| Pressure field microphone frequency response | 20Hz – 10kHz ± 0.5dB 10kHz – 16kHz ± 1dB |
| Sensitivity | 12.5mV (-38.0dB) ± 2dB |
| Sound pressure measurement range | 33dB(A) – 143dB (1000 Hz distortion <3%) |
| Interface | BNC |
| Main materials | Stainless steel |
| Operating temperature range | -20℃ to 60℃ |
| Relative temperature | 10-90% non-condensing |
| Storage conditions | Temperature: 25℃±5℃, Humidity: 50%±15%RH (to ensure long-term stability of the sensor) |
V. Conclusion
The MegaSig CM 311+A 803 is a modern artificial ear that inherits the classic IEC 711 standard that has stood for forty years.
For electroacoustic engineers, choosing this product is more than just buying a microphone; it’s introducing a “traceable standard” to your testing system. Whether it’s fine-tuning during the R&D phase or quality control during mass production, it provides stable, accurate, and internationally compliant measurement data. If you’re looking for a cost-effective solution that complies with IEC 60318-4, this product is your best choice.
Need further planning consultation for your project? Feel free to contact us anytime for technical discussions.