ATI HPSS
The ATI Soundblaster HPSS (high-power speaker station) is an electronic outdoor warning system manufactured by Acoustic Technology, Inc (ATI) that is used to alert the surrounding populace of tornadoes, hurricanes, severe thunderstorms, fires and so on. The recent HPSS systems use high-powered electronic speakers, which can be independently arranged to provide directional or omnidirectional coverage, depending on installation. The HPSS16 provides up to 1600 watts of continuous power to drive up to four 400-watt speaker units, whereas the larger 3200-watt HPSS32 can drive up to eight 400-watt speakers. Like other electronic outdoor warning systems (such as Federal Signal's Modulator, for example), they can also be used as public announcement (PA) systems, and can play a number of programmed tones. Options include solar-powered operation and pre-recorded voice messages. Sometimes these high-powered speakers play the Westminster Chime.
Areas known to use HPSS systems
- San Francisco, California - This system is unique, in that it features the sound of the decommissioned Federal Signal STL-10 sirens that the HPSS units replaced
- Casitas Dam, Ventura, California (This system is unique, in that they look like the Federal Signal Directional Speaker Array (DSA) sirens), but can have 7–8 speakers per stack, and gray caps on the speaker cones).
- Indian Point Energy Center, New York
- Owasso, Oklahoma - System of sixteen HPSS32 sirens.
- Israel has 3100 sirens as a part of its warning system, and 300 of them are HPSS32 sirens.
- Sedgwick County, Kansas 27 ATI HPSS32 units are part of the system's 150 sirens.
- Frisco, Texas ATI HPSS32 units.
- Fort Riley, Kansas 2 ATI HPSS16 units.
- Del City, Oklahoma 8 ATI HPSS16 units. Currently inactive until the infrastructure that programs the said sirens arrives.
- Pasig City, Philippines has 1 ATI HPSS32 unit.
Problems and criticism
Many deployed HPSS systems, with the exception of the most recent models (and the HPSS systems used in San Francisco, California), used a 1000 Hz Sine wave tone, which some allege is not sufficiently distinct against very noisy backgrounds, or over acceptable distances. More recent HPSS units use a lower-pitched 570 Hz tone which has given adequate results.
In San Francisco, many of their HPSS units have the tones of a Federal Signal STL-10 siren, which was one of the sirens used by San Francisco until the whole siren system was replaced with HPSS systems. While this added voice capability to San Francisco's warning network, it has also caused some reliability problems as the comparatively deep-pitched growl of these tones can damage the speakers when playing at high volume. However, this may not necessarily be the fault of the speakers used, as few electronic speakers can tolerate playing such low-pitched, bass-rich sounds at high volume levels for extended periods of time.