Stump Microphone and DRS Technology Explained: How Officials Use Technology
How stump microphones, UltraEdge, and Hawk-Eye technology work together in the Decision Review System (DRS) — what each technology detects, how they are used in review decisions, and why they have made dismissal decisions more accurate.
Modern cricket uses a suite of technologies to assist umpires in making accurate dismissal decisions through the Decision Review System (DRS). The primary DRS technologies are: Hawk-Eye (ball-tracking for lbw decisions), UltraEdge (audio-visual edge detection for caught-behind decisions), Hot Spot (infrared imaging for contact detection — not always in use), and stump microphones (ambient audio for detecting small sounds of contact). Each technology addresses a specific type of umpiring uncertainty that cannot be resolved by the naked eye.
Hawk-Eye Ball Tracking
Hawk-Eye uses multiple cameras to track the ball's trajectory from the bowler's hand to the point of impact with the batter or pad, then predicts where the ball would have continued. In lbw reviews, Hawk-Eye reconstructs the ball's path and predicts whether it would have hit the stumps if the pad had not been in the way. The prediction has a 2.5cm uncertainty zone around the stumps — deliveries predicted to be marginally hitting (within 2.5cm of the stumps) retain the original umpire's call (on-field umpire's call = not out), while deliveries clearly hitting retain the on-field decision only if there is genuine uncertainty in the original call.
UltraEdge
UltraEdge (formerly Snickometer, now enhanced) detects sound waves through a stump microphone and displays them as a waveform — when the ball passes the bat, any contact (edge, hit, or near-miss) generates a spike in the waveform. The third umpire examines the UltraEdge waveform synchronized to the ball's exact position — if a spike coincides with the ball passing the edge of the bat, it suggests contact (edge). UltraEdge cannot distinguish between ball-bat contact and ball-pad contact that occurs simultaneously — this is why Hot Spot infrared is sometimes used to confirm the specific point of contact.
Hot Spot
Hot Spot uses dual infrared cameras positioned at each end of the ground — when the ball contacts any surface (bat, pad, glove, body), friction generates a brief heat signature visible on the infrared feed. Hot Spot can confirm bat-ball contact that UltraEdge cannot distinguish from pad contact, and can identify very fine edges. However, Hot Spot is not always deployed — it is expensive and not mandatory for all international matches. When Hot Spot and UltraEdge disagree (one shows contact, one doesn't), the third umpire must weigh the evidence from both systems alongside the on-field decision.
Frequently asked questions
What technologies does DRS use to review decisions?
Hawk-Eye (ball trajectory for lbw), UltraEdge (waveform audio for edges), Hot Spot (infrared heat signature for contact), and stump microphones (ambient audio). Each addresses specific umpiring uncertainty: Hawk-Eye for lbw path prediction, UltraEdge/Hot Spot for caught-behind contact detection.
What is Hawk-Eye in cricket?
Ball-tracking technology using multiple cameras to reconstruct the ball's trajectory from bowling crease to point of impact, then predict where it would have gone. Used for lbw reviews to determine if the ball would have hit the stumps. Has a 2.5cm uncertainty zone where the on-field umpire's call is retained.
What is UltraEdge in cricket?
A stump microphone-based system that displays sound waves as a waveform. A spike in the waveform coinciding with the ball passing the bat suggests edge contact. Used for caught-behind and caught at slip reviews. Sometimes combined with Hot Spot (infrared) to confirm whether contact was bat or pad when UltraEdge shows a spike.