Handset Receiver Distortion: Harmonics, Rub and Buzz, and Fault Isolation
Calculate acoustic THD, distinguish harmonic distortion from rub and buzz, and improve receiver testing through controlled drive, coupling, noise and fault isolation.
Buzzer Testing: Drive Conditions, Sound Pressure and Background Noise
A practical guide to buzzer testing: define drive voltage and waveform, microphone distance and weighting, correct for background noise, and assess results after assembly.
Car Door Acoustics: Speaker Enclosure Volume, Leakage and Bass Response
Car-door bass depends on leakage, rear-cavity compliance and panel vibration. Ideal sealed-box calculations show how volume affects resonance, while practical tests separate door and cabin effects.
Loudspeaker Directivity: Diaphragm Size, Wavelength and Off-Axis Response
Explore how effective diaphragm diameter and wavelength shape off-axis response. Calculated piston examples explain angular losses, crossover integration and repeatable measurements in the final installation.
Air Ultrasonic Transducers: Impedance Mismatch, Matching Layers and Sealed Housings
PZT is about 34 MRayl and air about 413 rayl, so bare-ceramic transmission is only -43 dB. We derive the ideal 0.12 MRayl quarter-wave matching layer and its bandwidth cost, explain why 40 kHz sensors use flexural vibrators, compare open and closed types and size the tuning inductor.
How Magnetic Buzzers Work: Magnet Bias, Coil Inductance and Flyback Protection
A magnetic buzzer drives a steel diaphragm by magnetic attraction. We explain why a magnet bias is essential, then cover negative stiffness, resonance, coil impedance, square-wave drive current, the flyback diode and how magnetic and piezo buzzers compare.
Loudspeaker Sensitivity and Efficiency: 1 W, 2.83 V and the Reference Efficiency η0
Sensitivity may be quoted at 1 W / 1 m, 2.83 V / 1 m or 0.1 m, and a 4 Ω driver gains 3 dB at 2.83 V. We derive the reference efficiency η0 and the 1 W / 1 m level from T/S parameters, work through examples, and cover the Bl trade-off, distance scaling and datasheet checks.
How Handset Receivers Work: Pressure Fields, Acoustic Leakage and Ear-Simulator Testing
A receiver works in a pressure field: the same excursion is about 80 dB louder in a 2 cc ear cavity than in open air at 1 m. We cover construction and back-cavity stiffness, use the Helmholtz formula for leakage and front-cavity resonance, and explain ITU-T P.57 artificial ears and test conditions.
Matching Car Speakers to Amplifiers: 14.4 V Supplies, Bridged Outputs and 4 Ω Loads
A 12 V-class supply limits car amplifiers: an ideal 14.4 V bridge into 4 Ω clips at about 25.9 W. We compare single-ended and BTL outputs, explain max-power ratings, 4 Ω versus 2 Ω and dual voice coils, and quantify cable resistance and voice-coil heating.
How Piezo Buzzers Work: Resonance, Anti-Resonance and Three-Terminal Self-Drive
A piezo buzzer sounds because the converse piezoelectric effect bends a ceramic-on-metal laminate. We use the BVD model to explain resonance and anti-resonance, then cover square-wave and full-bridge drive, capacitive-load power, three-terminal self-oscillation and the housing's Helmholtz cavity.
Ultrasonic Ranging Explained: Time of Flight, Temperature Compensation and the Blind Zone
Ultrasonic ranging looks like speed of sound times time divided by two, but accuracy is limited by temperature drift, transducer ringing, echo attenuation and beam angle. Using a 40 kHz piezo sensor, we give the equations, worked numbers and engineering countermeasures.
Reading a Loudspeaker Impedance Curve: From DC Resistance to Thiele/Small Parameters
Impedance varies with frequency, and the curve reveals a loudspeaker's resonance, Q factors and voice-coil inductance. We explain the equivalent circuit, the three regions of the curve, T/S parameter extraction with a worked example, and practical uses in amplifier matching, cavity design and QC.
Summary of China's Loudspeaker Standards
Nine current Chinese loudspeaker standards and the older editions they replaced.
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Selection of speakers
The speaker system has a number of features that are directly related to the use