News

ShotSpotter system records tragic plane crash

First-time use of gun-shot detection system for a crash investigation, air officials say

First there is the sound of a plane's engines. Then a crackling noise, as though the plane has hit a power line. Then, crashing sounds, as parts of the aircraft landed on homes; a loud bang as the plane impacted with the ground; and a few seconds after the crash, people screaming as the plane fuselage skidded down Beech Street and plowed into walls and cars in the neighborhood.

The 11 seconds of Wednesday's plane crash into an East Palo Alto residential neighborhood were recorded by the city's ShotSpotter gun-shot detection system, East Palo Alto Police Chief Ronald Davis announced during a press conference on Thursday.

It is the first time in aviation history that such a recording will be used for forensic purposes, according to Joshua Cawthra, lead investigator for the National Transportation Safety Board (NTSB), which is looking into the causes of the accident.

Three Tesla Motors employees, pilot Doug Bourn and passengers Brian Finn and Andrew Ingram, were killed in the 8 a.m. crash one minute after takeoff from the Palo Alto Airport. The twin-engine Cessna 310R struck high-tension power lines and a transmission tower at the edge of the Baylands and then slammed into the Beech Street neighborhood. Parts of the plane hit homes, destroying one and damaging three others. No other persons were injured, officials said.

The gun-shot detection technology was developed by Mountain View-based company ShotSpotter. The system triggers only on loud, impulsive noises -- things that go "bang," according to James Bedlock, company president.

The recording starts a few seconds before the sound of the crash.

"When we heard that a plane had crashed in an East Palo Alto neighborhood, all of us at ShotSpotter knew there was a high probability the city's ShotSpotter Gunshot Location System had detected the incident. (Wednesday's) plane crash created such a noise and it did trigger more than one ShotSpotter sensor deployed in East Palo Alto," he said in a company statement.

ShotSpotter filters sounds to separate gun shots from other noise then reports the gunfire and location to police. The system automatically classified the crash as loud and impulsive but not gunfire and did not report the incident in real time to the East Palo Alto Police dispatch.

For forensic purposes, all loud, impulsive noises are logged by ShotSpotter systems, even if they do not trigger an automatic alert, in case those noises needed to be reviewed after-the-fact, he said.

"Once we determined that the system had registered a loud, impulsive, non-gunfire noise at the time of the crash, we assisted the East Palo Alto Police Department with the retrieval and storage of the audio captured by their system's ShotSpotter sensors for the seconds surrounding the impulsive noise (the crash).

"The East Palo Alto Police Department then provided that data to representatives of the National Transportation Safety Board to support their investigation of the crash," he said.

"Because the ShotSpotter sensors each contain a GPS receiver with a precision clock, the NTSB now has a precise, millisecond-by-millisecond recording of the incident, as captured by several ShotSpotter sensors deployed throughout East Palo Alto. In total, five ShotSpotter sensors generated data which contribute consistently to the mathematical location of the crash. The sensors were located at various distances from the crash, the closest being just over 600 feet away and the furthest being roughly 1,500 feet away," he said.

Cawthra said during a late afternoon press conference Thursday that the data will help analyze engine sounds, their vibration and speed and whether they were working properly at the time of the crash.

The private plane did not have a flight recorder as is required in commercial aircraft, so the ShotSpotter recording could be critical in assessing what happened, he said. No distress calls were received by the airport control tower, he said.

Both engines had been recovered and were being moved to Sacramento for analysis, he said.

Investigators had determined the plane's controls were working properly, he added.

The plane's wreckage was spread about 1,200 feet or the size of four football fields, he said.

A preliminary report will be available on the NTSB website within about five days, he said.

Around 5:30 p.m. on Thursday, the damaged PG&E utility tower was removed by helicopter in two pieces, flying over the San Francisco Bay.

PG&E spokesman Joe Molica said the damaged utility tower is being stored in a company construction yard in Newark and will be inspected by NTSB.

East Palo Alto installed the ShotSpotter system citywide in November 2008. Last month, the police department credited the system with decreasing firearm assaults by 29 percent from 2008, helped in addition by a greater community willingness to report crime. Read the Weekly's archived story on ShotSpotter.

Related stories:

Organizations to help residents after crash

Anna Eshoo visits crash site, expresses sorrow

Video/photos: Feb. 17 plane crash, power outage

Fire chief: 'It was a miracle' no residents died

Comments

Posted by Roy, a resident of Barron Park
on Feb 19, 2010 at 10:17 am

Big Brother is watching (or rather listening) to you. Beware!!


Posted by Steve, a resident of Menlo Park
on Feb 19, 2010 at 11:01 am

Roy -
Now don't go all paranoid on us.
If you're shooting off guns you should beware. As the story clearly explained, the system was designed for the single purpose of detecting and locating gunfire within the city and has succeeded in reducing illegal use of firearms. It can't hear, let alone trigger on, conversations even if you yell at the top of your lungs.
I hope you were joking.


Posted by Hank, a resident of Green Acres
on Feb 19, 2010 at 11:14 am

"the system was designed for the single purpose of detecting and locating gunfire within the city"

Apparently it was designed for that single purpose but it's now being used for more stuff like investigating airplane crashes. Just like Fastrak was designed for paying tolls but is now used to determine people's whereabouts and/or speeds between two sensors.


Posted by anonymous, a resident of Another Palo Alto neighborhood
on Feb 19, 2010 at 11:36 am

didn't you hear the report on npr this morning about the study using cell phone data to look at people's movements! we should all know that no one is anonymous now :)


Posted by Jack Bauer, a resident of another community
on Feb 19, 2010 at 11:43 am

Using cell phones to track people is nothing new. Last year, Sprint said that they released cell phone data to the police over 1 million times without any court order. They even built a special web site to make this easy for the police to do. I assume the other cell phone companies are doing the same thing (but not bragging about it). Your cell phone records includes the call information that appears on your phone bills and also location information (which cell tower you connected to). They are tracking your location even when you are not making a call.


Posted by Julian, a resident of Palo Verde
on Feb 19, 2010 at 12:05 pm

How about the promise made more than 70 years ago that the Social Security Number would never be used to identify individuals.

The road to hell is paved with good intentions.


Posted by T Tierney, a resident of Downtown North
on Feb 19, 2010 at 12:18 pm

The city government installed these systems with the promise that they could only trigger on gunshots. This shows that promise was a lie, that the government can rewind the recordings and listen to anything they want.

Big Brother is the only description.


Posted by qq, a resident of Barron Park
on Feb 19, 2010 at 12:35 pm

I love all the wording they use. Dance, dance, dance.

Basically what it does, without saying it in so many words; it records *everything* but only sends "alerts" for firearm discharge type sound triggers.

Perhaps we can start selling "Cones of Silence" to folks in EPA.

Web Link


Posted by don, a resident of Downtown North
on Feb 19, 2010 at 12:47 pm

Paranoia is alive and well. If you're not doing anything illegal, what is your problem? I doubt if anything you do or say legally is of any interest to the anyone much less the authorities. They're so overwhelmed and understaffed, they don't have time to snoop on essentially boring trivia.

We lost our privacy many years ago when the IRS began collecting income tax and the government began the New Deal programs and later, Medicare and Medical. Remember that your employer keeps records, too. And think of the people putting all their personal information on Facebook without a thought of who might use it. Etc., etc.

However, I do think that X-ray scanners at airports now are a bit much.


Posted by Max, a resident of Fairmeadow
on Feb 19, 2010 at 1:50 pm

qq:

what did you say?


Posted by Steve, a resident of Menlo Park
on Feb 19, 2010 at 5:01 pm

T Tierney- you wrote:
"This shows that promise was a lie, that the government can rewind the recordings and listen to anything they want."

Did you even read the article? Cause you clearly don't understand the technology. It's a solid state memory that is constantly writing over old data, unless a trigger tells it that a shot (or other impulsive sound, like a plane crashing) has occurred and to save that 10 or 20 seconds of data. There is no continuous recording and generally the sounds that are saved are not even listened to. Note that the article said the the ShotSpotter company had to help the EPA police with the recovery and storage of the audio. All they generally want is the time of the first impulse, which combined with times from other instruments lets them triangulate back to the source of the sound (gunshot) - much like earthquakes are located.

In fact the technology was first developed by a seismologist at USGS in Menlo Park who was concerned about all the random firing of guns in Redwood City. He figured that the same technology that measures P-waves to locate earthquakes could be used to measure sound waves to locate gunshots. He demonstrated the concept worked and then turned it over to private industry to perfect and market. Hence the company ShotSpotters and their very successful product. The Redwood City Police Department credits the ShotSpotter technology with enabling them "to prevent gunfire crimes, deaths and serious injuries from occurring.

Seems this a very useful application of science to solve a societal problem. Only the paranoid could spin it into the nefarious scenarios I've been reading here.

Don is right: "Paranoia is alive and well" - which bodes poorly for the health of a community where trust is as shallow as some people's intellect.


Posted by Sharon, a resident of Midtown
on Feb 19, 2010 at 5:30 pm

As Eric Emerson Schmidt CEO, of Google said recently

" If you are not doing anything illegal why should you worry about privacy "

In fact there is no privacy apart from medical records and then only up to a point, if you have contagious diseases you have no privacy anf insurance companies will base their rates on you health status.

The ShotSpotter recordings are amazing, and they have only released 11 seconds of them.
It is a great technology, deters and solves serious violent crime and now will help solve why the plane crashed, you can hear that both engines appear to be functioning normally before the crash, maybe the pilot had health problems--- should be know soon.


Posted by qq, a resident of Barron Park
on Feb 19, 2010 at 8:51 pm


'I've Got Nothing to Hide' and Other Misunderstandings of Privacy

DANIEL J. SOLOVE
George Washington University Law School

Abstract:
In this short essay, written for a symposium in the San Diego Law Review, Professor Daniel Solove examines the nothing to hide argument. When asked about government surveillance and data mining, many people respond by declaring: I've got nothing to hide. According to the nothing to hide argument, there is no threat to privacy unless the government uncovers unlawful activity, in which case a person has no legitimate justification to claim that it remain private. The nothing to hide argument and its variants are quite prevalent, and thus are worth addressing. In this essay, Solove critiques the nothing to hide argument and exposes its faulty underpinnings.

Web Link


Posted by parent, a resident of Barron Park
on Feb 20, 2010 at 12:15 am

Steve,

Yes, we read the article and you're the one that obviously doesn't understand the technology. The ability to recover sounds hours after Mr Bourn's crash into a neighborhood full of families and their children indicates that the device has a fairly significant amount of storage. As a solid state device, the storage firmware almost certainly does "wear leveling". This means that the most recent data isn't actually deleted, but just marked available for later use. The firmware does this to lengthen the life of the solid state storage which has a finite number of write cycles. Plenty of criminals have been convicted using evidence that they thought had been long deleted. It's certainly possible that much more information still resides on the recording device. Anybody who's accidentally deleted a picture from a digital camera knows that.

It's ironic that you try to school us in the origins of the technology. But, using audio recordings to reconstruct incidents is at least as old as the plane Mr Bourn's was flying. The most famous case is the purported "acoustic evidence" (since debunked) that the House Select Committee used in finding a conspiracy in the Kennedy
assassination. Is there a more perfect example of the government going overboard with the mis-application of acoustic technology?


Posted by Steve, a resident of Menlo Park
on Feb 20, 2010 at 2:14 am

Parent -
The ability to recover sounds hours after the event doesn't tell us anything about how much storage this system has. It's an event-triggered system that only saves sound for a short period of time around the time of the trigger, which is usually a gunshot. The six seconds of audio can be recovered at anytime after the event - even hours - but that doesn't means hours of audio are recorded.
The clip we heard from the accident was one of these triggered 6-second clips. Perhaps the ShotSpotter techs could have recovered other audio from the device but that is clearly not easily done or we would have heard more than just the 6 seconds - the sounds from the accident were still very loud when the clip terminated.
My main point is that a lot of people posting here are way paranoid and infer nefarious government motives behind fairly straightforward and appropriate procedures. Instead of applauding the use of a technology that has reduced death & injury from illegal gunfire and (BONUS!) may help in the investigation of this horrible accident, these folks are seeing CIA-type plots & interventions. Taken to an extreme, these folks become Timothy McVeeigh types who bomb government buildings and fly their planes into IRS offices, convinced they're saving us from Big Brother, a term that was actually used in an above post.
Paranoia is a sickness and even in low level cases like these posts, it degrades the health of our democracy. As someone smarter than me has noted "Whatever we expect with confidence becomes our own self-fulfilling prophecy."


Posted by common sense, a resident of Meadow Park
on Feb 20, 2010 at 6:48 am

All this blah blah blah about "nothing to hide" and "storage" etc..

but in the end it doesn't matter what it was intended for, how it was built, etc.

What matters is the result: Which is anybody can rewind and listen to a "good reason" to anything recorded by this device.

In this case..ok..fine..we give up some privacy for locating gun shots or figuring out what went wrong to cause this tragedy.

But, we must be mindful of the fact that with these advantages, along with the advantages of cell phones, video recordings, internet tracking etc.. we are ever closer to big brother, no matter how you splice it.

Who was it that said all good things can be perverted to evil? We have certainly seen this proven throughout history.


Posted by Steve, a resident of Menlo Park
on Feb 20, 2010 at 11:05 am

Common Sense- You write
"What matters is the result: Which is anybody can rewind and listen to . . .anything recorded by this device."

Obviously not or we would have heard more than the 6-second clip of the accident. If even the techs who sell & service these devices couldn't pull out more than this, your statement is patently false. The only things available to listen to are the 6-seconds of audio recorded at the time of the trigger (gunshot, backfire, plane crash). If you say something treasonous during this 6-second window and you're near enough to one of the mics to be be recorded you might have something to worry about. Common sense should tell you that the chances of this are essentially zero.


Posted by Neal, a resident of another community
on Feb 20, 2010 at 11:34 am

Steve,

Please indicate where you learned the storage capacity of the device. The manufacturer's website (Web Link) seems to indicate that audio is recorded continuously and retained on the local device. When a sensor on the device is triggered by a loud, acoustic impulse, a snippet of the locally-stored audio, beginning "a few seconds" before and after the event (in this case, at least eleven seconds), is automatically uploaded to the main system and the operator. It does not indicate whether the operator can recall audio from the device at will or how much data is stored on the device. It indicates that the device picks up and forwards conversations in 10% of the triggered events, but that these conversations are not intelligible using the system's audio playback. It does not indicate whether this audio may be enhanced using other products.


Posted by Steve, a resident of Menlo Park
on Feb 20, 2010 at 1:08 pm

Neal -

I got the "6-second clip" info from a paper on the ShotSpotter website

Web Link

that explained:
"A snippet of 6 sec of data is stored for subsequent analysis when a gunshot or other impulsive noise is located, and this data can be played back through speakers so that the dispatchers can ascertain the nature of the sound to determine if they will dispatch to it."

The paper was written in 1997 so things may have changed but I didn't read anything about continuous recording. It's certainly possible that continuous data is recorded but, because it's an event triggered system, only the 6-second clips are actually saved and acted on. Any continuous recording would not be easily recovered.
The acoustic devices that pick up the sounds (mics) are very widely spaced, usually on roofs and telephone poles, and aren't capable of recording conversations in any useful way.


Posted by Neal, a resident of another community
on Feb 20, 2010 at 2:01 pm

Steve, thanks for the info; it helps in trying to piece together what this system is. The device must be a continuous recorder, as the company's website (FAQ section) says, "The audio usually starts a few seconds before the [triggering] sound." The question then is how much data the device stores before rewriting itself. Unless the PAO article is incorrect, it must store at least eleven seconds—and probably more than that. The six seconds you spotted in the company paper must just be the default snippet size sent to the operator (unless the specification has changed). It looks like the operator is able to remotely access the recording device and override the default snippet size of six seconds to download larger, longer files. This indicates the operator can, at will, remotely review the device's recording file.

The company (FAQ section) says that the recording quality is similar to that of a cell phone. I do not know how far the recording was from the scene, but, even after reformatting for web release, the quality was good enough to make out syllables, articulated screams, etc. If the recording were made at night without background noise and close to the source, the recordings might be intelligible.

Since the devices' purpose is solely to detect gunshots, either the device hardware should be modified to not allow recording prior to or long after a triggering sound (e.g., a noise gate—Web Link), or the recording should be automatically, irreversibly distorted (e.g., using microphones w/ altered/damaged diaphragms). These modifications should be made at the hardware level to alleviate public mistrust.


Posted by Steve, a resident of Menlo Park
on Feb 20, 2010 at 2:10 pm

Neal -
thanks for your web link on the ShotSpotter website. They answer this question of "Big Brother" directly. Quoting from their FAQ page:
"In rare cases (less than a few tens of incidents out of the literally hundreds of thousands of incidents our customers' systems have detected and downloaded), the sounds of human voices —children playing in a playground, for example, but not the actual words spoken because the voices are too far away—can be heard in the background when these incidents trigger. (The recent tragic plane crash in East Palo Alto is an example of an impact noise which did cause our nearby sensors to trigger. Nonetheless, note that none of the voices of the children is intelligible.) It is important to note that at the distances at which our sensors detect gunfire (hundreds to thousands of feet away), human voices are not intelligible. In fact, typical human speech is not intelligible at distances greater than 20 feet away from our acoustic sensors. (Technical detail: we use the same microphones used in many cell phones. Try this experiment yourself: use your cell phone to call your own voicemail from an outdoor location, walk 20-30 feet away and speak in a normal voice. When you play back the voicemail, you won't be intelligible.) ShotSpotter sensors are typically deployed far off the ground, most often on building rooftops near the air conditioning vents and other "rooftop fixtures." Thus sensor locations are specifically chosen to avoid the possibility of individuals being overheard: these are locations to which access is restricted. These locations conveniently also are ones where the sensors do hear what they are supposed to hear: gunfire and other loud, impulsive noises at great distance. (To put it another way, if you want to listen for gunfire, you will have better luck standing on a building rooftop than sitting on a street corner.)"
"Perhaps more importantly, we've gone to great lengths not to implement features which could be used to invade privacy. We have made sure that our customers cannot use the system for eavesdropping. In addition to the fact that the sensors simply cannot hear intelligible speech because of where they are placed and the fact that they only automatically download a few seconds of audio even when they do trigger, there are other safeguards. We don't give the customer a "listen live" feature in our wireless sensors for two reasons: (1) we left this feature out so that there could be no privacy concerns; and (2) if we were to implement it, the feature would probably swamp our wireless network itself! (In general, ShotSpotter sensors are deployed on relatively low bandwidth networks which simply could not sustain continuous transmission of audio. This is an intentional design limitation designed to help ensure privacy. It also keeps the price down."

This should reassure anyone but the most paranoid.


Posted by Steve, a resident of Menlo Park
on Feb 20, 2010 at 2:27 pm

Neal -
Yes the length of the continuous recording is a question, though it may be irrelevant if the quality of the audio precludes actually understanding any voices, as they claim.
However you write:
"The device must be a continuous recorder, as the company's website (FAQ section) says, "The audio usually starts a few seconds before the [triggering] sound." The question then is how much data the device stores before rewriting itself."

It's equally plausible that they simply use something like the "profanity delay" circuits talkshows use to allow them to bleep swear words before they are broadcast. There's no actual recording going on, other than the temporary 1 to 5 second of looping audio in volatile memory.


Posted by Neal, a resident of another community
on Feb 20, 2010 at 3:24 pm

Steve,

This is exactly the problem: the public does not have enough information to allay privacy concerns. A system designed w/ built in hardware limitations is more appropriate for public deployment. Limiting the hardware to allay these concerns is an insignificant cost (< $100 per square mile in a system costing $200,000 per square mile). Frankly, it's a little creepy that these this was not addressed in design: the device is meant to improve the quality of life of all members of the public. The "paranoid" and those w/ privacy concerns are members of that public; where some of those concerns can be easily addressed, they should be addressed.


Posted by Steve, a resident of Menlo Park
on Feb 20, 2010 at 4:36 pm

Neal -
Having read the ShotSpotters FAQ I feel that Ihave enough information to allay my privacy concerns.
First, by design, any voices inadvertently recorded in their short clips are unintelligible.
Second, only the short clips are actually downloaded and playable by the dispatchers.
Third, they intentionally did not include the ability to listen live to the microphones.
I'm comfortable that they've taken privacy concerns into account in the design of their system.


Posted by One of the "most paranoid", a resident of Meadow Park
on Feb 20, 2010 at 7:55 pm

Me thinks somebody works for or has an investment in ShotSpotters to so vehemently deny the valid concerns of others.


Posted by Steve, a resident of Menlo Park
on Feb 20, 2010 at 11:24 pm

One of the most paranoid -
I think you are referring to me.
Sorry to disappoint but I have no connection to the company at all. I didn't even know about ShotSpotters until they were mentioned in the press as a result of the crash on Tuesday.
I do know how earthquakes are recorded and located and its very similar to the techniques ShotSpotters employ. I also read their documents and they make perfect sense to me. I see no reason to think there's any more to it than meets the eye.
I know its fashionable in some circles to be suspicious & cynical about anything any government does but I think it's not at all helpful and is a large part of why our state & federal governments are floundering at the moment. When a sizable proportion of the people question everything the government does, is it any wonder that we can't seem to deal with the big problems that confront us?
As I said above, paranoia is a sickness. It seems to be spreading.


Posted by One of the most paranoid, a resident of Meadow Park
on Feb 21, 2010 at 6:05 am

Steve, this isn't a "fashionable" person writing this response, it is one steeped in history, thus quite knowledgeable of the unintended consequences of giving to others the power over your own life...be it the power to hear you, track you, seize your property or earnings, jail you, draft you, "give" you food, clothing, housing, a job ..whatever the power is in the name of "good intentions", is what the road to hell is paved with...ending a sentence with a preposition notwithstanding.

It may be "fashionable" to wear a coat in the winter, but it stems from years of experience in protecting yourself from the elements, right?

Never forget, if the government can "give", it can "take away" also, and it will, the moment it becomes either fashionable or bankrupt enough to do so. ( ask anyone who was dependent on "govt" to help them through hard times what is happening right now)






Posted by One of the "most paranoid", a resident of Meadow Park
on Feb 21, 2010 at 6:13 am

[Post removed by Palo Alto Online staff.]


Posted by Steve, a resident of Menlo Park
on Feb 21, 2010 at 9:47 am

"One of the most Paranoid"
You say I insulted you by calling you paranoid. Hello. What name did you choose for yourself?
At least you recognize the problem. The next step is getting counseling. You'll be happier for it.
From Wikipedia:
"Paranoia is a thought process heavily influenced by anxiety or fear, often to the point of irrationality and delusion. Paranoid thinking typically includes persecutory beliefs concerning a perceived threat towards oneself."
I may be looking through rose-colored glasses but I'd rather that than to see treachery everywhere.


Posted by One of the most paranoid, a resident of Greenmeadow
on Feb 21, 2010 at 11:22 am

Interesting, calling a poster "sickly paranoid" is not deleted, but what is deleted is a response that states the person who commented on "sick paranoia" may not have outgrown his baby fat of naivete and therefore needs to be understood.

Well, Steve, have fun continuing the insults all by yourself...




Posted by musical, a resident of Palo Verde
on Feb 22, 2010 at 2:37 am

Yeah, next thing you know these paranoids will say our laptop cameras can be used to spy on us in our own bedrooms. I'm sure the episode at that Pennsylvania high school is just an isolated incident. Nevertheless, I'm taping a piece of aluminum foil over this camera lens right now.


Posted by T Tierney, a resident of Downtown North
on Feb 22, 2010 at 5:39 pm

Wow, my post got insulted several times since I last checked in!

Another paper (Web Link) gave an audio player to let readers hear recordings from two of the recorders. Somebody was able to rewind those machines and retrieve what they wanted. The recordings the city supplied is 11 seconds long, so the claim of six seconds is not correct.

I suspect that neither the city nor the company that makes these things would let a trustable engineer review the actual operation of them. I fear we would find that the recordings are continuous until overwritten weeks later, and that loud sounds cause the alerts but are independent of the recordings.

What we know is that it seems pretty easy to get whatever recordings the engineers want.


Posted by Steve, a resident of Menlo Park
on Feb 23, 2010 at 11:25 am

T. Tierney -
Your link doesn't support your statements. It only shows 2 clips recorded by 2 audio sensors. Doesn't look, as far as I can tell from the link, that there was any rewinding of anything - just the triggered clips, which are generated automatically and sent to the dispatcher for review.
The 6-seconds was my mistake - it was the length of recording mentioned in a 1997 publication ShotSpotters had on their website that described the length of the recording used at the time. Either they changed it to 11 seconds or, because the loud noises of the crash continued for many seconds (unlike a gunshot) it stayed in record mode longer. The techs at ShotSpotters could probably say.
Bottom line - both recordings are clips recorded automatically by the trigger - you still have shown me no evidence to support your claim "that it seems pretty easy to get whatever recordings the engineers want."


Posted by T Tierney, a resident of Downtown North
on Feb 23, 2010 at 12:53 pm

Steve,

I would be happy to have you prove me wrong. Please do.


Posted by Steve, a resident of Menlo Park
on Feb 23, 2010 at 1:50 pm

T Tierney -

I'll look into it and see what I can find out.


Posted by Steve, a resident of Menlo Park
on Feb 23, 2010 at 11:13 pm

T Tierney -
Nothing definitive but here's a line from a letter from a ShotSpotter employee on their website. Web Link He expresses the company's condolences to all affected by the crash and then goes on to explain how the company helped recover the audio clips for the NTSB investigators. This is the pertinent information:

"As with all audio associated with a ShotSpotter incident, the audio we assisted the East Palo Alto Police Department in providing to the NTSB starts a few seconds before the sound of the crash (providing the sound of the engines), includes the sound of the crash itself, and a few seconds after the crash."

Elsewhere on their website they address the issue of privacy:
Web Link

"Privacy rights are an issue of utmost importance to ShotSpotter. We have spent tremendous time and effort designing our gunshot location systems in order to ensure the privacy rights of every citizen."

"Our sensors trigger only when a loud, impulsive sound is detected. .
. Human speech is incapable of producing such sounds; hence our sensors are unable to be triggered by . . . the human voice"

"When an impulsive sound occurs-such as gunfire, a firework, or an explosion noise . . . our system automatically downloads a brief audio clip of the incident. The audio clip lasts only a few seconds and usually starts a few seconds before the sound and ends a few seconds after."

"We've gone to great lengths to ensure that our technology cannot be used to eavesdrop and invade privacy. Despite misinformation, there is no "listen live" feature in our wireless sensors for two reasons: (1) we are dedicated to preserving personal privacy (2) ShotSpotter sensors are deployed on relatively low bandwidth networks which could not sustain continuous transmission of audio."

"In extremely rare cases, the sounds of loud human voices can be heard in the background after an impulsive incident has triggered our system. In all of these cases, only the sound of voices can be heard, not the actual words. This is because sensors are typically deployed on building rooftops, far off the ground and away from public access. In short, we deploy our sensors too far away. . . In fact, typical human speech is not intelligible at distances greater than twenty feet away from our acoustic sensors as we use the same microphones used in most cell phones.


Posted by T Tierney, a resident of Downtown North
on Feb 24, 2010 at 2:59 pm

Steve,

Thanks for going to the work of researching it.

T


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