Doppler Simulation

It is well known that a time-varying delay line results in a frequency shift. Time-varying delay is often used, for example, to provide vibrato and chorus effects [20]. We therefore expect a time-varying delay-line to be capable of precise Doppler simulation. This section discusses simulating the Doppler effect using a variable delay line [477].

Consider Doppler shift from a physical point of view. The air can be considered as analogous to a magnetic tape which moves from source to listener at speed (see Fig.3.10). The source is analogous to the write-head of a tape recorder, and the listener corresponds to the read-head. When the source and listener are fixed, the listener receives what the source records. When either moves, a Doppler shift is observed by the listener, according to Eq.(3.4).^4.4

---

Subsections

• Doppler Simulation via Delay Lines
• Time-Varying Delay-Line Reads
• Multiple Read Pointers
• Multiple Write Pointers
• Stereo Processing
• System Block Diagram

---

Order a Hardcopy of Physical Audio Signal Processing

Previous: Vector Formulation
Next: Doppler Simulation via Delay Lines

---

written by Julius Orion Smith III
Julius Smith's background is in electrical engineering (BS Rice 1975, PhD Stanford 1983). He is presently Professor of Music and Associate Professor (by courtesy) of Electrical Engineering at Stanford's Center for Computer Research in Music and Acoustics (CCRMA), teaching courses and pursuing research related to signal processing applied to music and audio systems. See http://ccrma.stanford.edu/~jos/ for details.