When selecting an electronic siren, the primary technical metric is the Sound Pressure Level (SPL), typically measured in decibels (dB) at a distance of 1 meter. For industrial environments, look for units providing 110dB to 120dB to ensure audibility over ambient noise. Additionally, verify the IP Rating (Ingress Protection); for outdoor or harsh industrial use, a minimum of IP65 or IP66 is essential to protect against dust and high-pressure water jets. You should also consider the number of selectable tones (e.g., 32 or 64 tones) to allow for different alert levels within a single system.