Audio Engineering Interactive
Interactive models and graphics on sound, audio and acoustics – free to use for teaching and self-study.
I am Jan-H. Kramer and I teach media technology and audio engineering at Osnabrück University of Applied Sciences. The modules were made for my course: you can turn the controls, watch and listen instead of only reading formulas. I would be glad if others use them in their teaching too – freely and at no cost, with attribution. How to use them
No module matches this filter.
Signals and sound
What sounds are made of: kinds of sound, fundamental, overtones and waveform.
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Kinds of Sound: Tone, Complex Tone, Noise and Bang
The four kinds of sound after DIN 1320 compared: waveform, line or continuous spectrum, periodicity, pitch and crest factor – with inharmonic tone mixtures, noise colours and a bang to listen to.
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Harmonic Series
Build sounds from sine waves: weight the harmonics freely or load sine, sawtooth, square and triangle – with waveform, keyboard and distortion figures.
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Hearing and psychoacoustics
How hearing perceives levels and frequencies – loudness and masking.
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Decibels and phons
Compare sound pressure level and perceived loudness in the equal-loudness diagram: drag tones, change the level, read phon and sone.
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Masking and masked threshold
A loud tone or noise makes quieter tones nearby inaudible – in the spectrum and shortly before and after. Drag maskers and test tone and read the masked threshold.
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Filters
Analogue filters and equalisers, illustrated as oscillating spring–mass systems.
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Spring–Mass System as a High-Cut Filter
A signal drives a spring–mass system. How sluggishly the mass follows determines which frequencies pass: a second-order low-pass filter.
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Spring–Mass System as a Low-Cut Filter
The signal moves a housing in which a mass hangs on a spring. The motion of the mass relative to the housing is measured: low frequencies vanish, high ones pass – a second-order high-pass filter.
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Bell Filter (Peaking EQ)
A spring–mass resonator is mixed into or subtracted from the direct signal. This creates a boost or cut around the centre frequency – just like a parametric equaliser.
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Shelving Filter (Low and High Shelf)
The same spring–mass resonator as in the bell filter, tapped differently: the position or inertial force of the mass plus the damper force are mixed into the direct signal. This boosts or cuts all low or all high frequencies – just like bass and treble controls.
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Pre- and De-Emphasis (RIAA, FM, CD, Tape)
The treble is boosted before the medium and cut by the mirror image afterwards: the signal arrives unchanged, while hiss and crackle become quieter. With the RIAA curve of the vinyl record, FM, CD emphasis and tape equalisation – also to listen to.
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Digital signal processing
Sampled signals: digital filters, phase response and spectrum analysis.
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FIR Filter (Digital Filter)
The signal is sampled, runs through a delay line and is summed with weighting coefficients. The coefficients can be dragged freely with the mouse.
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Pre-Ringing: Linear Phase vs. Minimum Phase
Two digital low-pass filters with almost the same frequency response – but the linear-phase filter starts ringing before the edge arrives. The play cursor shows what happens when.
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Forward-backward filtering (filtfilt)
A minimum-phase filter applied once backwards and once forwards: the phase shifts cancel and the result is symmetric – with pre-ringing. Step by step.
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FFT: From Signal to Spectrum
How an analyser computes a spectrum from N samples: frequency resolution, leakage, window functions and aliasing to explore.
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Dynamics
Controlling levels automatically: compressor, limiter and their signal paths.
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Compressor and limiter
Try threshold, ratio, knee, attack, release and lookahead on test signals: transfer curve, gain reduction and levels live.
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Compressor signal paths
Switch between feed-forward, feedback, sidechain, parallel, multiband and stereo link in a block diagram and compare them.
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Effects
Modulation effects that change sound through delay and multiplication.
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Flanger, chorus and phaser
Compare three modulation effects with one switch: moving notches in the frequency response, delay line or all-pass chain, LFO and feedback.
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Ring modulator
Input times carrier: sum and difference frequencies in the spectrum, the multiplication over time, the transition to AM and tremolo and why the sound becomes inharmonic.
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