The Tannoy THL-1 tunnel loudspeaker provides a robust, durable and highly cost-effective solution for Emergency Voice Alarm/Communication (EVAC) systems in the physically and acoustically hostile environment of road tunnels. In an application notorious for high ambient noise levels and excessive reverberation, the THL-1 transmits crisp, controlled and intelligible voice announcements throughout the space from a minimum number of loudspeaker locations. The THL-1 is also built to withstand the corrosive atmospheric contaminants, high moisture levels and temperature extremes typically encountered in road tunnels.
Voice alarm systems in lengthy tunnel applications demand very high levels with low distortion to overcome both the surrounding ambient noise and the sound isolation of the vehicles while maintaining high speech intelligibility, with an average rated SPL output of 135db. To project an effective voice alarm notice over distances of up to 50 metres, the THL-1 incorporates an asymmetrical AFEX (Architectural Flare Extension) horn which leverages the acoustical properties of the tunnel wall to effectively extend the waveguide effect for greater directivity and increased propagation along the horn axis. Because the THL-1 carries intelligible voice notifications over greater distances, fewer loudspeakers are required, resulting in significant cost savings.
The THL-1 is designed to withstand the rigors of long-term exposure to harsh environments, and also to function reliably even in proximity to catastrophic fire and explosive events. Cable entry to the driver/transformer housing is tightly sealed by rubber grommets, and an AirNet backing behind the stainless steel grille prevents moisture ingress to the horn. The AFEX horn is constructed from thick, fire-retardant, multi-layer fiberglass to DIN4102 Class B standard. The ceramic cable connectors are rated to withstand temperatures to 600° C. To facilitate confidence testing at regular intervals as well as during emergencies, the THL-1 accommodates fault monitoring (in conjunction with external equipment) to the EN 54 standard.
The THL-1 installs quickly and securely using six mounting holes for fixing to threaded rods or bolts attached to the tunnel soffit or unistrut.
(Jim Evans)
