Reader-supported. GopherTrunk is free, open-source software. Some
hardware links on this page go to Amazon with our Associates tag
(gophertrunk-20); if you buy through them we may earn a small
commission at no extra cost to you. Links to out-of-production gear may go to
eBay searches instead; we have no affiliate relationship with eBay and earn
nothing there. It never changes which gear we recommend, and
the software stays free either way. How GopherTrunk is funded →
What Was That Loud Boom? How to Find Out
A boom big enough to make you search for it made other people call 911 — and within about two minutes a unit is dispatched to “check the area,” which means the fastest answer is hearing what that unit finds. Here’s the suspect list, the fast lookups, and how to tell the harmless booms from the call-911 ones.
Key takeaways Boom + power flicker = transformer/fuse fault → utility outage map (power outage near me). Boom + ground shake = check USGS “Did You Feel It?” — quakes, blasting, and sonic booms all show up there. Boom + nothing = fireworks, exploding targets, blasting, or a gunshot you’re unsure about. The verdict: the “area check” dispatch and its outcome, live on a scanner feed or your own scanner. Gas smell, smoke, or damage → 911.
The suspect list
- Transformer / fuse fault — gunshot-to-cannon bang, often a flash and a block losing power. The outage-map check confirms it in one look.
- Fireworks mortars & exploding targets — single deep booms from a distance, evenings and weekends, rural echo. Kin to the gunshots-or-fireworks question.
- Quarry / construction blasting — weekday, daytime, often felt as a thump then heard; permitted and scheduled, frequently the answer to “recurring 11 a.m. boom.”
- Vehicle strike — a car into a building, pole, or dumpster sounds exactly like an explosion one street over; this one will draw sirens.
- Sonic boom — military supersonic flight or a spacecraft reentry; rattles windows across tens of miles. Pairs with military jets overhead.
- Frost quake (cryoseism) — the coldest-night special: ground cracking with a rifle-crack boom and a very local shake.
- Earthquake / gas explosion — the two you rule out first when there’s shaking plus damage or a gas smell: USGS for the first, 911 for the second.
The five-minute lookup
- Utility outage map — did a block just go dark? Transformer. Done.
- USGS “Did You Feel It?” (earthquake.usgs.gov) — earthquakes post within minutes, and sonic-boom reports cluster there too, tagged as non-earthquakes.
- The dispatch radio — booms generate 911 calls; a county feed carries the “loud explosion reported, checking the area” run and, crucially, the outcome: “fireworks debris located,” “transformer down,” or “nothing found.”
- Local social media — a wide-area boom lights up town groups across several ZIP codes in minutes; purely local posts point at something on your block.
- Next morning: if you slept on it, reconstruct it from the CAD log and feed archives.
After a very close boom: the five-minute walk-around
If it sounded like it was on your property, check before you shrug:
- Nose first: any gas smell at the meter, water heater, or stove means everyone out, then call 911 from outside — no switches, no phones indoors, no restarting anything.
- Breaker panel: a tripped main plus the bang points at an electrical fault — leave it off and have it looked at rather than resetting blind.
- Walk the outside: scorch marks at the service drop, a hanging line (treat as live), damaged siding or roof edges, debris in the yard.
- Note the exact time from your phone or cameras — it lets neighbors, the utility, and the CAD log correlate your boom with everyone else’s, which is how one-street mysteries actually get solved.
When a boom is a 911 call
A gas smell, smoke, debris, damage, or people hurt — call, immediately. Explosions with consequences are exactly what the fire service wants early reports on. Everything else on this page is for the boom that leaves nothing behind but your curiosity — which is the usual kind, and the kind the radio answers while everyone else is still posting question marks.
The fix for next time: a scanner that never sleeps, for about $250
Every lookup method on this page depends on someone else — a feed volunteer, an app's coverage map, an agency webmaster. This kit removes the middleman: a silent little box on a shelf that decodes your county's digital dispatch directly off the air, streams it to any browser in the house, and records every call with timestamps. Next time the sirens go past, the answer is already on your phone — and free, open-source GopherTrunk is the software, so the parts below are the entire cost.
Why two receivers: one dongle stays locked to your police trunked system while the second covers fire/EMS or a neighboring system at the same time — the two channels a "what's going on?" moment actually needs. That's a trick a $500 handheld scanner can't do, and GopherTrunk drives both dongles from one Orange Pi.
Orange Pi 5
around $90
The RK3588 host that runs it all 24/7 — silent, low-power, and strong enough for both dongles with headroom to spare. GopherTrunk ships a native ARM64 Linux build for it.
Orange Pi 5 on Amazon →RTL-SDR Blog V4 kit
around $55
The dongle and the telescopic dipole antenna kit with coax and mounts in one box — this one holds your police system's control channel.
V4 + antenna kit on Amazon →RTL-SDR Blog V4 (second dongle)
around $35
Covers fire/EMS, a second trunked system, airband, or NOAA weather — simultaneously, not by giving up the first channel.
RTL-SDR V4 on Amazon →The complete parts list
| Part | Why it's in the kit | Approx $ | |
|---|---|---|---|
| Orange Pi 5 | Always-on host for both dongles | ~$90 | Amazon → |
| RTL-SDR Blog V4 + dipole antenna kit | Receiver #1, antennas, coax, mounts | ~$55 | Amazon → |
| RTL-SDR Blog V4 (second) | Receiver #2 — fire/EMS or a second system | ~$35 | Amazon → |
| Powered USB 3.0 hub | Clean, stable power for two warm dongles | ~$35 | Amazon → |
| 16-piece SMA adapter kit | Joins any antenna to any dongle, first try | ~$18 | Amazon → |
| RG316 SMA pigtail kit | Flexible jumpers between hub, dongles, antennas | ~$15 | Amazon → |
| USB-C power supply (5V/4A+) | The Orange Pi 5 needs solid power for 24/7 duty | ~$15 | Amazon → |
| microSD card (64GB, A2) | OS plus months of recorded calls | ~$12 | Amazon → |
Kit total: about $250–275. Worthwhile upgrade once it's earned a permanent shelf: an outdoor discone antenna (~$40) that hears everything from 25–3000 MHz — see the antenna guide. Prefer a Raspberry Pi 5 host instead? Same build, swap the board — Pi 5 (8GB) on Amazon and the SBC build guide.
From boxes to first decoded call
- Flash 64-bit Linux (Debian/Ubuntu image) to the microSD and boot the Orange Pi headless.
- Plug in the powered hub, both dongles, and the antennas — the adapter kit bridges any connector mismatch.
- Install GopherTrunk — one free static binary, no dependencies: download, then follow the setup guide to point it at your county's system from RadioReference.
- Open the web console from any phone or laptop in the house — live calls, talkgroup names, and a scrollable, replayable recording archive.
Two honest caveats before you spend a dime: check RadioReference that your agencies are not encrypted — no device decodes AES — and skim the legality rules for your state (listening is legal in the US; a few states restrict use in vehicles). Rather have a no-computer, pocketable option instead? That's the dedicated scanner guide.
Frequently asked questions
What was the loud boom I just heard?
The usual suspects, roughly in order of frequency: an electrical transformer or fuse fault (often with a power flicker), fireworks or exploding rifle targets, quarry or construction blasting, a vehicle crash, a sonic boom from military aircraft or a spacecraft reentry, and in cold snaps a frost quake. A house-shaking boom with no power blink and no sirens afterward is most often distant blasting, a sonic boom, or an exploding target.
How can I find out what a boom was?
Fast checks: your utility’s outage map (transformer faults usually take a block down), USGS ‘Did You Feel It?’ for anything that shook the ground, a county scanner feed — booms generate 911 calls, so listen for the ‘loud explosion, area check’ dispatch and what units find — and local social media, where a genuinely wide-area boom lights up posts across several towns within minutes.
The boom shook my whole house — should I be worried?
Shaking with a persistent gas smell, smoke, debris, or any damage: call 911. Shaking alone, with nothing following, is common for sonic booms, blasting, and frost quakes — air-pressure events rattle windows across miles. If dispatch sends units and they find nothing (the usual radio outcome), it was almost certainly one of those.
What is a frost quake?
A cryoseism — water-saturated ground freezing rapidly during a hard cold snap cracks with a gunshot-like boom and a local shake. They cluster on the coldest nights of the year, are harmless, and generate a wave of confused 911 calls that you can hear being triaged on the dispatch radio.
Was that a sonic boom? Who do I even ask?
Sonic booms come from supersonic military flight (usually over designated areas or offshore) and from spacecraft reentries, which can boom across a whole region. Check flight trackers for military activity, news for a scheduled reentry, and USGS — sonic booms often register as a ‘not an earthquake’ event. Military bases sometimes acknowledge supersonic training after the fact.
Booms keep happening in my area at random — what are they?
Recurring daytime booms on weekdays are usually permitted quarry or construction blasting — schedules are public record and your county often posts them. Recurring evening or weekend booms are typically fireworks or exploding rifle targets (Tannerite) on rural property. A scanner tells you whether anyone is dispatched and what they find each time.