Nonlinear Distortion Explained

Content Summary

This article provides a detailed introduction to Nonlinear Distortion, explaining its causes in accordance with the national standard GB/T 2900.86-2009, and analyzing its specific manifestations in dynamic microphones, condenser microphones, and wireless microphones. By integrating content from “Detailed Explanation of Distortion,” “Detailed Explanation of Harmonic Distortion,” and “Detailed Explanation of Fundamental Frequency,” this article explains the impact of nonlinear distortion on audio quality and how to reduce distortion through technical means to enhance the overall performance of audio systems.

Nonlinear Distortion: Signal Deformation Issues in Audio Systems

In audio systems, nonlinear distortion refers to the phenomenon where the input signal and output signal no longer maintain a linear relationship. This not only causes sound distortion but may also introduce new frequency components, altering the original audio's spectral structure.

According to the national standard GB/T 2900.86-2009:

"The output signal does not maintain a linear relationship with the input signal. Note: Distortion caused by nonlinearity introduces new frequency components into the output signal, altering the original signal's spectrum."

This article will explore the types, causes, and specific impacts of nonlinear distortion in dynamic microphones, condenser microphones, and wireless microphones from an audio engineering perspective, helping you understand its role in audio systems.

1. Basic Concepts of Nonlinear Distortion

1. Definition and Core Characteristics

Nonlinear distortion refers to: when an audio signal passes through a system, due to the nonlinear characteristics of the equipment, the output signal waveform undergoes “deformation,” causing the sound to no longer faithfully reproduce the original input.

For example:

A singer sings a clear mid-frequency note;

If the microphone picks up additional frequency components in the sound;

These extra components are the result of nonlinear distortion;

2. Main Types of Nonlinear Distortion

1. Harmonic Distortion

The presence of integer multiples of the input frequency (e.g., 2f₀, 3f₀) in the output signal, which is a subcategory of nonlinear distortion.

2. Intermodulation Distortion (IMD)

When multiple frequencies are input into the system simultaneously, nonlinear effects generate new frequency components (e.g., f₁ + f₂, f₁ - f₂).

3. Clipping Distortion

When the input signal exceeds the system's Dynamic Range, the output signal is “clipped,” resulting in waveform distortion.

3. Common Causes of Nonlinear Distortion

1. Microphone Overload

When a microphone is exposed to high Sound Pressure Levels, the diaphragm or preamplifier may fail to respond accurately, leading to signal distortion.

For example:  

Dynamic microphones may experience magnetic saturation when recording drum kits;  

Condenser microphones may lack clipping protection in their preamplifiers;  

This results in a significant amount of nonlinear components in the output signal;  

2. Wireless Transmission Compression  

Some wireless microphone systems use digital compression algorithms to transmit audio, which may cause signal waveform distortion.

For example:

Using a Bluetooth microphone for podcast recording;

If the encoding quality is low;

Some dynamic details may be lost;

Resulting in a lack of layered sound quality;

3. Component aging or poor quality

Low-quality capacitors, resistors, operational amplifiers, and other components are prone to introducing nonlinear distortion.

4. Nonlinear distortion characteristics in different microphone types

1. Dynamic Microphones

Dynamic microphones are known for their durability, but they are prone to nonlinear distortion in high-sound-pressure environments.

Mr Senma S-ONE Dynamic Vocal Microphones

a) Signal distortion caused by magnetic circuit saturation

When the input Sound Pressure is too high, the magnetic field may reach saturation, preventing the coil from continuing to move.

Result:

The output signal is “clipped”;

resulting in a noticeable “clicking” sound or harshness;

b) Frequency response limitations causing spectral distortion

Dynamic microphones typically have good mid-frequency response but limited ability to capture high-frequency harmonics.

For example:

The Shure SM58 has a frequency response upper limit of 15 kHz;

for vocals or string instruments rich in harmonics, this may cause an imbalance in the spectral structure;

2. Condenser Microphones

Condenser microphones have high sensitivity and a wide frequency response, but they are also more susceptible to electronic noise and overload.

Mr Senma A7 Small Diaphragm Condenser Microphones

a) Waveform clipping caused by preamp overload

Condenser microphones rely on internal preamps to amplify signal strength. If the input signal is too strong (e.g., plosive sounds, close-miking), the preamp may clip.

For example:  

Recording vocals without a pop filter;  

Causing sudden airflow to impact the microphone capsule;  

Resulting in noticeable distortion;  

b) Changes in spectral structure due to high-frequency response  

Condenser microphones can capture higher-frequency harmonic components, but if not handled properly, they may introduce unwanted spectral changes.  

For example:  

When a female singer sings high notes;  

If the microphone is overly sensitive to high-frequency response;

which may make the sound harsh;

3. Wireless Microphones

Wireless microphones must not only address traditional distortion issues but also deal with interference and compression problems during wireless transmission.

Mr Senma k58s portable Wireless microphones

a) Signal distortion caused by radio frequency interference

Wireless microphones operate in the UHF or VHF frequency bands. If there are other wireless devices nearby (such as Wi-Fi, Bluetooth, or walkie-talkies), this may cause signal interference.

For example:  

At large-scale events;  

Multiple wireless microphones used simultaneously;  

If channels are improperly configured;  

May result in frequency overlap or dropouts, manifesting as fluctuating volume, hoarseness, or intermittent sound;  

b) Dynamic range compression distortion caused by compression algorithms  

To conserve bandwidth, some wireless systems use compression encoding, which may cause sound to become “flat.”  

For example:  

Using a Bluetooth microphone for podcast recording;

If the encoding quality is low;

Some dynamic details may be lost;

Resulting in a lack of layering in the sound;

5. How to measure and control nonlinear distortion?

1. Measurement methods

Use an audio analyzer (such as APx500, SoundCheck);

Input a single-frequency sine wave (such as 1 kHz);

Analyze the harmonic and intermodulation components in the output signal;

Derive the THD and IMD percentage values;  

2. Control Strategies  

a) Properly set gain and PAD switch  

Avoid overloading the microphone preamplifier, especially when recording high-pressure sound sources, by enabling the PAD (attenuation) function.  

b) Use a pop filter and shock mount  

Reduce the impact of plosive sounds on the microphone capsule and lower the risk of clipping.

c) Optimize the wireless transmission environment  

Use radar frequency scanning to avoid interference bands and ensure stable transmission.  

6. Nonlinear distortion is a critical issue in audio systems  

Whether it is a dynamic microphone, condenser microphone, or wireless microphone, nonlinear distortion (nonlinear distortion) affects audio quality.

From the stability of the fundamental frequency to the integrity of the frequency spectrum, every stage can be a source of nonlinear distortion. Only through scientific selection, proper use, and proper maintenance can nonlinear distortion be minimized to the greatest extent, restoring true, clear, and natural sound.

As a professional Microphone Manufacturer, we have fully considered nonlinear distortion control mechanisms in the product design stage to ensure that every product delivers exceptional audio performance in various usage scenarios.