Introduction to Audio Analyzers

 Introduction to Audio Analyzers

An audio analyzer is a specialized electronic test instrument used to measure and evaluate the performance of audio systems and components such as amplifiers, microphones, loudspeakers, and digital audio devices. It works by sending a known test signal (stimulus) into

a device under test (DUT) and comparing the output signal with the original to determine parameters like distortion, noise, frequency response, and signal-to-noise ratio. 

Modern audio analyzers are essential in industries such as broadcasting, telecommunications, consumer electronics manufacturing, and acoustic research. They are designed to provide extremely accurate measurements with very low internal noise and distortion levels, ensuring reliable testing of high-quality audio equipment. 

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Working Principle of Audio Analyzers

The basic principle behind all audio analyzers is signal comparison and analysis:

1. A test signal (sine wave, square wave, noise, etc.) is generated.

2. This signal is passed through the device under test (DUT).

3. The analyzer captures the output signal.

4. It compares input and output to calculate differences such as distortion, noise, and frequency response. 

Key measurable parameters include:

• Total Harmonic Distortion (THD)

• Intermodulation Distortion (IMD)

• Signal-to-Noise Ratio (SNR)

• Frequency response

• Phase and crosstalk

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Types of Audio Analyzers

1. Analog Audio Analyzers

Description

Analog audio analyzers are the earliest type of audio measurement instruments. They use purely analog electronic circuits such as oscillators, amplifiers, and filters to generate and analyze signals.

Working Principle

• Operate using continuous electrical signals (analog signals).

• Use analog oscillators to generate test tones.

• Employ analog filters (band-pass, notch filters) to isolate frequencies and measure distortion or noise. 

Key Features

• Simple architecture

• Real-time continuous signal processing

• Limited flexibility compared to digital systems

Advantages

• Low latency (instantaneous response)

• Good for basic measurements

Limitations

• Less accurate for complex analysis

• Limited ability to process multiple parameters simultaneously

• Susceptible to noise and drift

Example Brands & Models

• Hewlett-Packard (HP 8903B) – classic analog analyzer

• Bruel & Kjær analog analyzers

• Tektronix analog audio test systems

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2. Digital Audio Analyzers

Description

Digital audio analyzers represent modern instrumentation that uses digital signal processing (DSP) techniques to generate and analyze audio signals.

Working Principle

• Convert analog signals into digital form using Analog-to-Digital Converters (ADC)

• Process signals using DSP algorithms such as Fast Fourier Transform (FFT)

• Generate signals digitally using Digital-to-Analog Converters (DAC) 

Key Features

• High precision and repeatability

• Ability to analyze complex signals

• Software-based flexibility

Advantages

• Extremely accurate measurements

• Multi-channel analysis

• Advanced visualization (graphs, spectra)

Limitations

• Slight processing delay (latency)

• Higher cost

Example Brands & Models

• Audio Precision (APx555, APx585) – industry standard

• Rohde & Schwarz (UPV, UPP analyzers)

• Keysight Technologies (U8903A)

• Prism Sound (dScope Series III) 

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3. Real-Time Audio Analyzers (RTA)

Description

A Real-Time Analyzer (RTA) is a specialized audio analyzer that continuously displays the frequency spectrum of an audio signal as it happens.

Working Principle

• Breaks the audio signal into multiple frequency bands

• Displays amplitude vs frequency in real time

• Uses either:

  • Analog filter banks, or

  • Digital FFT-based processing 

Key Features

• Instant visualization of sound spectrum

• Used in live sound, acoustics, and sound system tuning

• Displays levels in frequency bands (octaves or fractions of octaves)

Advantages

• Immediate feedback

• Useful for sound equalization and room acoustics

• Helps identify feedback and frequency imbalance

Limitations

• Less precise than full lab analyzers for detailed measurements

• Resolution depends on number of frequency bands

Types of RTAs

1. Analog RTAs – use band-pass filters

2. Digital RTAs – use DSP and FFT algorithms 

Example Brands & Software

• NTi Audio (XL2 Analyzer)

• Behringer (DEQ2496 with RTA)

• Smaart (software analyzer)

• Room EQ Wizard (REW)

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Applications of Audio Analyzers

Audio analyzers are widely used in:

• Audio equipment manufacturing

• Broadcast and studio engineering

• Telecommunications

• Acoustic research and noise analysis

• Live sound system tuning

They help engineers ensure that audio devices meet required standards and deliver high-quality sound performance.

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Conclusion

Audio analyzers are indispensable tools in modern audio engineering. From analog analyzers with simple circuitry to advanced digital analyzers using DSP and real-time analyzers for live monitoring, each type serves a specific purpose. Understanding their working principles and differences helps engineers choose the right instrument for applications ranging from laboratory testing to live sound optimization.

Manufacturers of Audio Analyzers

Manufacturers of Sound Level Meters