Safe Speed Forums

Why don't emergency services have what is known in electronics as a 'soft start' on their alert tones?

My work base is in and around a hospital complex and I often find myself walking down the streets when suddenly, without any warning, an ambulance starts the alert next to where I'm walking and I nearly $h1t myself!!!

I don't mean to be crude, but if you have ever had this happen to you, you will know EXACTLY what I mean. Not only do I think it's dangerous but it could well be detrimental to your hearing too.

A soft start, as its name implies, would start at a lower volume, maybe for a second or less, just to let people know it's about to kick-off and allow you to prepare or adjust. I'm sure that a short delay wouldn't make all that much difference to the driver if he is looking ahead, as indeed he should of course, but it would make all the difference to me and let's not forget they have the conventional horn if needs must demand an immediate alert.

Fire engines in the West Midlands have a double alert - the American style 'weee wooo' siren thing coupled with an equally deafening horn which would happily grace the QEII. What's then hell is that about? It's louder than a Motorhead concert!

So then, my suggestion - a soft start.

Come on Paul - I deserve at least an 8 this time eh?

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The views expressed in this post are personal opinions and do not necessarily represent the views of Safe Speed.
You will be branded a threat to society by going over a speed limit where it is safe to do so, and suffer the consequences of your actions in a way criminals do not, more so than someone who is a real threat to our society.

not a great idea, the siren is likely to be used to wake up some dozey sod who hasn't seen the big van with the disco lights, now if it starts quietly people will assume it is further away than it is,

No no dave - honest. That isn't how the soft start principle works. It gives a short, very short, time for pedestrians to prepare. I would agree with you if it were to build up over, let's say, several seconds. But I'm talking about a fraction of a second.

It's the difference between me blasting a horn down your ear or doing the same with my hand over the horn before removing my hand. It just gives you enough time to cover your ears or for your own body's natural response to defend itself. Ya know?

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The views expressed in this post are personal opinions and do not necessarily represent the views of Safe Speed.
You will be branded a threat to society by going over a speed limit where it is safe to do so, and suffer the consequences of your actions in a way criminals do not, more so than someone who is a real threat to our society.

I'm not sure - the rapid rise in sound pressure level at the start of the envelope may help the sound to be recognised when it is quieter and more distant (or masked by loud music, or whatever).

I'm very interested in technologies that help you to pinpoint the source of the sound. When bells gave way to two tones it was very highly noticable to me that I couldn't tell where the two tones were coming from (whereas with the bells it was easy). I'm quite sure that the main reason was to do with the rich harmonics of the bell sound. With less harmonic content in the two tones standing wave effects could give nonsensical direction information. Modern sirens are much better in this respect, but still worse than the bells (IMO) for direction information.

Perhaps we could solve your original 'startle' problem with a warning tone? Sort of 'pip WAHHHH'? We'd still get the potential benefit of the sharp rise in SPL when the main sound starts.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

I agree with the bells. The modern type, although very piercing, don't have quite the same sense of distance and direction I think.

My idea comes from my days in electronics engineering; the soft start term comes from Power Supply Units I worked on where instead of blowing up the main power transistors by delivering the full current in an instant, instead it ramps-up to full power over a pre-determined time thereby saving the circuit from failure.

The circuit in this case is my ears and heart. I have jerked so violently in the past that I have given myself a crick in the neck. Maybe funny to some, but not nice in reality to those who have experienced it and who's to say it may not be worse for others of a weaker, more nervous, disposition?

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The views expressed in this post are personal opinions and do not necessarily represent the views of Safe Speed.
You will be branded a threat to society by going over a speed limit where it is safe to do so, and suffer the consequences of your actions in a way criminals do not, more so than someone who is a real threat to our society.

And 'pip WAHHHH'?

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

Can you send me a WAV file and I'll see if I like it?

Maybe if it gets approval it will generate some useful funding

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The views expressed in this post are personal opinions and do not necessarily represent the views of Safe Speed.
You will be branded a threat to society by going over a speed limit where it is safe to do so, and suffer the consequences of your actions in a way criminals do not, more so than someone who is a real threat to our society.

Anyone got a modern siren .wav to work from?

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

I don't see why an additional pip WAHHH is necessary when a simple modification of the existing alert, (soft start), would do exactly the same thing.

I think we're singing from the same hymn sheet. Ahem...

We plough the fields and scatter
Good cameras on the land,
But it is fed and watered
By Gov's almighty hand…

By the way, it's possible to have an electronic bell of course so if that really does work better then maybe that's another good idea?

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The views expressed in this post are personal opinions and do not necessarily represent the views of Safe Speed.
You will be branded a threat to society by going over a speed limit where it is safe to do so, and suffer the consequences of your actions in a way criminals do not, more so than someone who is a real threat to our society.

I think soft start would make the sound far less noticable / distinguishable when it is feint or distant.

Which it what I explained, and why I came up with 'pip WAHHHH'.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

NO NO. That's not what I mean. It's meant to be less noticable, that's the whole point. But only for less than a second, like I said at the begining, while it alerts people nearby that the sound is about to go ape - up to full song! Ya know?

Oh - I got it. You'd do anything not to give me an 8.

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The views expressed in this post are personal opinions and do not necessarily represent the views of Safe Speed.
You will be branded a threat to society by going over a speed limit where it is safe to do so, and suffer the consequences of your actions in a way criminals do not, more so than someone who is a real threat to our society.

It's like me saying, "hey Ralph I'm going to fire a shotgun" and then firing the shotgun.

You would know where and how far each noise is, but the first prepares you for the second.

Honest. I know what I'm saying.

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The views expressed in this post are personal opinions and do not necessarily represent the views of Safe Speed.
You will be branded a threat to society by going over a speed limit where it is safe to do so, and suffer the consequences of your actions in a way criminals do not, more so than someone who is a real threat to our society.

I'm sorry you're not understanding me. I'm trying to say again and again that I believe the steep attack of the envelope is important to recognition when the sound is feint and / or distant.

'pip WAHHH' gives you your warning when the source is close yet preserves the steep attack.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

I understand but I'm not sure that I agree that the initial "steep attack" is factual?

I know it's a different situation but it happens at my work place when every Friday at 9 a.m. there's a fire alarm drill. It's exactly what I'm rying to describe here and presumably it's just as important or potentially urgent? Everyone knows exactly where it's coming from but it doesn't make everyone throw their coffee in the air.

It begins with a meow and builds to a roar after a few seconds. What I'm suggesting is something similar but only with a shorter delay.

What does a pip WAHHH do that as soft start doesn't?

Awe - now you've beaten me into submission.

_________________
The views expressed in this post are personal opinions and do not necessarily represent the views of Safe Speed.
You will be branded a threat to society by going over a speed limit where it is safe to do so, and suffer the consequences of your actions in a way criminals do not, more so than someone who is a real threat to our society.

I've gotta go home now, but I'm going to learn more about this steep attack.

I have another friend/work colleague (oh no) who's an ex sound engineer of 16 years. He's been with us in the NHS for years now but has worked all over the planet with the likes of Kylie, Prince etc. (I'm such a name dropper) and has probably forgotten more than we'll ever know about sound.

Maybe we can get him on board. I know he feels the same way as us on the scamera deal.

On the surface it seems like you are saying people cannot discern between a soft sound that's close by and a loud sound that's far away. (soz if I'm wrong there)

I'll sleep on it...

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The views expressed in this post are personal opinions and do not necessarily represent the views of Safe Speed.
You will be branded a threat to society by going over a speed limit where it is safe to do so, and suffer the consequences of your actions in a way criminals do not, more so than someone who is a real threat to our society.

I'm sure I heard something some years ago about research into "white noise" sirens because human ears can't pinpoint the direction from high higher frequency sound is coming from. Dunno what became of it though.

Is it important that people can tell where the siren is when it starts up? Quite often they will have had the siren on further away then you could hear it. I don't recall being able to tell where it is coming from from the first noise I hear.
And if someone is in their way they tend to lean on the horn anyway.

I'm pretty sure I have heard a white noise generator siren. I think it worked well too. But it was a long time ago. Where they went I don't know.

I wish they had a volume control. That would be useful.

I have had an ambulance turn its siren on while I was walking down the road. I even watched it come up the hill and still jumped. I'm sure people have had heart attacks from less.

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Andrew.

My point exactly And rather than make it more complicated you could easily, and cheaply, overcome this by a soft start.

I wish I could demonstrate what I'm on about. I'll see if I can create a WAV to send as a demo. I'm on a mission now...

_________________
The views expressed in this post are personal opinions and do not necessarily represent the views of Safe Speed.
You will be branded a threat to society by going over a speed limit where it is safe to do so, and suffer the consequences of your actions in a way criminals do not, more so than someone who is a real threat to our society.

fairly sure they trialled these in leeds a number of years ago.... it sounded liek a regular siren sound with blasts of broader frequency white noise overlayed....

....and as a pedestrian you could hear them and immediately turn your head in the right direction to see them, not always the case with regular nee-naa

White noise, for people who don't know, is a term used in electronics and sounds like the noise you get when you are between radio stations. Not sure how you would spell it but maybe a shsssssss?

It was used as a method of torture in WWII. You blindfold someone, force them to stand against a wall with their hands up against the wall and make them wear headphones with white noise constantly playing. It disorientates you and eventually sends you mad. A bit like working for the NHS

_________________
The views expressed in this post are personal opinions and do not necessarily represent the views of Safe Speed.
You will be branded a threat to society by going over a speed limit where it is safe to do so, and suffer the consequences of your actions in a way criminals do not, more so than someone who is a real threat to our society.