Legendre-tapered spherical transducer caps achieve constant beamwidth above a cut-off frequency
Evidence
Keele (2000, 2002, 2003a & b) extended the work of Van Buren (Rogers and Van Buren, 1978; Van Buren et al., 1983) to develop the constant beam width theory (CBT) arrays. In his papers, the transducer is a circular spher ical cap of arbitrary half-angle with Legendre function shading. It provides a constant beam pattern and directivity with extremely low side lobes for all frequencies above a certain cut-off frequency. … To maintain constant beamwidth behavior, CBT circular-arc loud speaker line arrays require that the individual transducer drive levels be set according to a continuous Legendre shading function. This shading gradu ally tapers the drive levels from maximum at the center of the array to zero at the outside edges of the array. — David Howard, Jamie Angus, coustics and Psychoacoustics, 2900
Categorization
Category: Definitional Content
- DEFINE: Introduces the CBT array concept and its defining Legendre shading mechanism.
Related
- Legendre-tapered drive levels give spherical-cap arrays constant beamwidth with low side lobes (similarity 0.95)
- CBT arrays taper drive levels from center to edges for constant beamwidth (similarity 0.88)
- CBT arrays achieve constant beamwidth using only level shifts, not complex frequency-dependent processing. (similarity 0.85)
- Curved, Legendre-shaded line arrays exploit floor reflections to maintain constant beamwidth at all frequencies (similarity 0.85)
- CBT arrays need only frequency-independent level shifts, unlike conventional line arrays (similarity 0.83)
- Curved and Legendre-shaded loudspeaker lines use the floor reflection to achieve uniform broadband coverage. (similarity 0.83)
- Constant beamwidth transducers deliver uniform sound levels over large areas (similarity 0.81)
- Constant-beamwidth-transducer speaker arrays hold stable loudness across listening distance (similarity 0.80)
- Curved CBT arrays need no frequency-dependent signal processing (similarity 0.80)
- Constant Beamwidth Transducer loudspeakers produce astonishingly uniform sound level across listening distance. (similarity 0.79)
Broader Connections
- CBT arrays taper drive levels from center to edges for constant beamwidth
#expands(0.85) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2914 - Digital signal processing made constant-directivity array loudspeakers practical and popular
#expands(0.75) — David Howard, Jamie Angus, coustics and Psychoacoustics, 2486 - Practical audio devices rest on underlying acoustics principles
#exemplifies(0.70) — David Howard, Jamie Angus, coustics and Psychoacoustics, 13