Hissing sounds on the letter S
Mark C Hudson
Why is it that the letter S when broadcast can be prone to make your radio
(usually) or TV go all hissy?
This doesn't happen on the infinitely inferior telephone, so why on radio &
TV?
Incidentally I notice it doesn't happen as much these days, but does anyone
want to offer a technical explanation as to what is causing it?
Mark
--
--
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Mike Brown
Mark C Hudson wrote:
>
> Why is it that the letter S when broadcast can be prone to make your radio
> (usually) or TV go all hissy?
>
> This doesn't happen on the infinitely inferior telephone, so why on radio &
> TV?
>
> Incidentally I notice it doesn't happen as much these days, but does anyone
> want to offer a technical explanation as to what is causing it?
Well, I don't know about 'technical', I'll try and keep it simple...
Unlike most vocal sounds the 'S' consists of a broad spectrum of
frequencies, many of which are quite high. Higher frequencies cause
equipment to have to work faster, so this sibilence (to give it its
correct term) is more prone to distortion than any other part of speech
because of the demands it makes on the equipment.
Under ideal conditions there would be no distortion of the signal, but
things are often far from ideal, either at the source or at the
receiver. The hissing you refer to is actually high frequency
distortion, which may be caused by anything anywhere in the signal path
such as a faulty microphone, an overloaded tape recorder or, very often,
by the fact that your radio is not delivering a perfect signal to your
receiver, as will often be the case with an (FM) car radio.
This kind of distortion often happens with music as well, but people
know what speech should sound like so they're usually more critical when
it sounds wrong.
The problem frequently does occur with telephones as well but the
severely restricted bandwidth (frequency response) of the telephone
(i.e. the fact that it is infinitely inferior!) lessens how much it
bothers us.
It can also happen quite badly with vinyl records too (if you remember
them?!)
The fact that you are noticing the problem less these days may be due,
in part, to the increasing use of digital audio technology (e.g. Compact
Disc, NICAM etc.) which is virtually immune from this type of problem.
(How am I doing, boffins?)
Hope this helps.
___________________________________________________________________
_ _ _ _
|\/|||/|_ |_)|_)/ \| ||\ | Audio CD pre-mastering engineer, disc
| |||\|_ |_)| \\_/|/\|| \| cutting specialist and...Andrew's dad
___________________________________________________________________
Martin Underwood
Mike Brown (m...@enterprise.net) wrote:
: Mark C Hudson wrote:
: >
: > Why is it that the letter S when broadcast can be prone to make your radio
: > (usually) or TV go all hissy?
: >
: > This doesn't happen on the infinitely inferior telephone, so why on radio &
: > TV?
: Unlike most vocal sounds the 'S' consists of a broad spectrum of
: frequencies, many of which are quite high. Higher frequencies cause
: equipment to have to work faster, so this sibilence (to give it its
: correct term) is more prone to distortion than any other part of speech
: because of the demands it makes on the equipment.
: Under ideal conditions there would be no distortion of the signal, but
: things are often far from ideal, either at the source or at the
: receiver. The hissing you refer to is actually high frequency
: distortion, which may be caused by anything anywhere in the signal path
: such as a faulty microphone, an overloaded tape recorder or, very often,
: by the fact that your radio is not delivering a perfect signal to your
: receiver, as will often be the case with an (FM) car radio.
: This kind of distortion often happens with music as well, but people
: know what speech should sound like so they're usually more critical when
: it sounds wrong.
: The problem frequently does occur with telephones as well but the
: severely restricted bandwidth (frequency response) of the telephone
: (i.e. the fact that it is infinitely inferior!) lessens how much it
: bothers us.
I've always wondered why the effect is far more pronounced with VHF radio
than with TV sound (analogue FM, not NICAM). Even when I play my crappy
10-year-old video through my hi-fi, there's rarely any hiss or sibilance,
whereas VHF radio (with stereo turned off, to compare like with like) is
usually sibilant (especially female newsreaders and continuity announcers
on Radio 4). Does Radio 4 employ sibilant newsreaders :-) It's not nearly
as noticeable on other stations (LBC, Capital, GLR, 210 FM).
Mike Brown
Martin Underwood wrote:
>
> I've always wondered why the effect is far more pronounced with VHF radio
> than with TV sound (analogue FM, not NICAM). Even when I play my crappy
> 10-year-old video through my hi-fi, there's rarely any hiss or sibilance,
> whereas VHF radio (with stereo turned off, to compare like with like) is
> usually sibilant (especially female newsreaders and continuity announcers
> on Radio 4). Does Radio 4 employ sibilant newsreaders :-) It's not nearly
> as noticeable on other stations (LBC, Capital, GLR, 210 FM).
TV usually mics up 'talking heads' with clip-on lapel mics, which offers
several practical advantages, but in pure audio terms is not quite so
good. One by-product of this is that such mics usually pick up less
sibilence.
Radio, at it's best (e.g. Radio 4!), is usually less compromising, so
producing a signal which is actually more demanding.
If you live in the London area have you tried retuning from Wrotham to
the new(ish) transmissions from Crystal Palace? CP is 0.3MHz below
Wrotham, so R4 is on 93.2MHz.
--
Richard Lambley
In article <542drc$7...@ozz.oasis.icl.co.uk>, Martin Underwood
<URL:mailto:m...@oasis.icl.co.uk> wrote:
>
> Does Radio 4 employ sibilant newsreaders :-) It's not nearly
> as noticeable on other stations (LBC, Capital, GLR, 210 FM).
World Service used to have a wonderfully sibilant one, of treasured memory
(teeth were the problem there). But I think the explanation may lie in the
current tendency to close-mic everybody, producing a rather different
acoustic balance from the natural sound at a normal hearing distance. A
decade ago, the practice was to have a distance of a script-and-a-half
between mouth and mic.
Another factor may be the high-frequency pre-emphasis on FM transmissions. To
avoid over-deviating the TX with HF-rich programme material, it's necessary
to have fast limiters. Modern digital limiters won't introduce distortion in
the sense of clipping the audio waveform, but driving them with high speech
levels (as even R4 does nowadays) could cause them to alter its character
in a possibly unnatural way.
Richard
--
Steve Simpson
>
>: This kind of distortion often happens with music as well, but people
>: know what speech should sound like so they're usually more critical when
>: it sounds wrong.
>
>: The problem frequently does occur with telephones as well but the
>: severely restricted bandwidth (frequency response) of the telephone
>: (i.e. the fact that it is infinitely inferior!) lessens how much it
>: bothers us.
>
>than with TV sound (analogue FM, not NICAM). Even when I play my crappy
>10-year-old video through my hi-fi, there's rarely any hiss or sibilance,
>whereas VHF radio (with stereo turned off, to compare like with like) is
>usually sibilant (especially female newsreaders and continuity announcers
>as noticeable on other stations (LBC, Capital, GLR, 210 FM).
Has anyone noticed the very low frequency rumble on certain announcers
on R4. I think it may be a cheap studio thing but I wouldn't mind any
other comments.
--
Steve "Chubby" Simpson
HTML Programmer/Night Club D.J.
Telephone No. - +44 (0)1707 394974
E-Mail Alias - Chu...@usa.net
Amateur Packet - G7NAY@GB7MSW.#33.GBR.EU
Internet URL - http://www.chubs.demon.co.uk
Marc Remijn
In <542drc$7...@ozz.oasis.icl.co.uk> m...@oasis.icl.co.uk (Martin
Underwood) wrote:
>Mike Brown (m...@enterprise.net) wrote:
>: Mark C Hudson wrote:
>: >
>: > Why is it that the letter S when broadcast can be prone to make
your radio
>: > (usually) or TV go all hissy?
>: >
[...]
>
>I've always wondered why the effect is far more pronounced with VHF
radio
>than with TV sound (analogue FM, not NICAM). Even when I play my crappy
>10-year-old video through my hi-fi, there's rarely any hiss or
sibilance,
>whereas VHF radio (with stereo turned off, to compare like with like)
is
>usually sibilant (especially female newsreaders and continuity
announcers
>on Radio 4). Does Radio 4 employ sibilant newsreaders :-) It's not
nearly
>as noticeable on other stations (LBC, Capital, GLR, 210 FM).
I think this is due to the far greater bandwidth of the TV audio signal.
VHF radio is 150 kHz while TV audio is 300 kHz, which means more 'room'
for high signal peaks or high frequencies, both of which occur with
's-es'.
Marc
--
__
/| /| | /
_____/ |/ | | \____ NL-5913 CX VENLO
Marc | |Remijn +31-77-3520099
Andrew Virnuls
Martin Underwood wrote:
>
> I've always wondered why the effect is far more pronounced with VHF radio
> than with TV sound (analogue FM, not NICAM). Even when I play my crappy
> 10-year-old video through my hi-fi, there's rarely any hiss or sibilance,
> whereas VHF radio (with stereo turned off, to compare like with like) is
> usually sibilant (especially female newsreaders and continuity announcers
> on Radio 4). Does Radio 4 employ sibilant newsreaders :-) It's not nearly
> as noticeable on other stations (LBC, Capital, GLR, 210 FM).
I'd imagine that the difference is sound quality, between FM radio and FM
television is due to your equipment, as speech sounds less sibilant on the
radio with my tuner, although it is a lot more detailed than the sound
produced by the hi-fi video.
As for the Radio 4/ILR comparison, surely they're completely different
anyway? Most local radio presenters sound like they're shouting at you down
a drain-pipe, whereas you can hear Radio 4 presenters breathing and smacking
their lips together, and even making notes (at least that's what it sounds
like) with the squeaky pens that they seem to use on the Today programme.
While we're on Radio 4, has anyone else noticed an annoying background
whistle during the 6 o'clock news? It's far more noticeable in the car for
some reason. I thought that perhaps it was caused by some sort of
mis-tuning or interference, but it always seems to stop at 6.30.
--
___ _ _ ____ ___ __ __ __ .--------------------------------------.
/ _ \| \| | _ \| _ \ __\ \ / / | Dr Fact is knocking at the |
| _ | .` | |_) | / _| \ \/\/ / | door, someone please let |
|_| |_|_|\_|____/|_|_\___| \_/\_/ | the man in! |
'--------------------------------------'
Martin Angove
Andrew Virnuls wrote:
>
> While we're on Radio 4, has anyone else noticed an annoying background
> whistle during the 6 o'clock news? It's far more noticeable in the car for
> some reason. I thought that perhaps it was caused by some sort of
> mis-tuning or interference, but it always seems to stop at 6.30.
>
It's almost definately not the same thing but at Red Dragon we
have both high frequency whistling *and* low frequency rumble, if
you listen closely enough. The HF is the line scan (hands up if
your hearing is too dead to hear it) from the TV in the studio
(it's getting on a bit), and the LF is because the mic boom is
screwed to the cart machine housing (are we the only people still
using carts?), and if all four are 'ready to go' chances are that
you can hear some bearing rumble.
Before anyone says it, yeah, I know the line scan is 15.6ish kHz
and FM radio is supposed to be 15 kHz, but I really can hear it -
especially if the jock's watching teletext. On the same subject,
we're said to have filters that will deal with the LF, but I'm
blowed if I can't hear it.
Mind you, most of the time the mic is closed so neither is
audible. On top of that, the number of times when the mic is
open, there's no music bed, and the jock is speaking sufficiently
quietly to hear either is, how shall we say this... not very
many.
--
Martin Angove
Yma o hyd.
Keith Hayler
The reason for the 'hissing' distortion being more noticeable
on VHF radio and TV broadcasts is that these media both use a
technique called 'pre-emphasis'.
VHF radio and UHF TV use Frequency Modulation which has an
unfortunate side effect of the background reception noise
increasing with frequency. In order to overcome this the
higher audio frequencies are boosted upon transmission to lift
them above the noise. Upon reception the inverse filter
characteristic is used to restore a flat audio frequency
response whilst reducing the noise as well!
The only problem with this technique is that, because they are
boosted by several dB for transmission, high frequency sounds
are more likely to push system elements into overload.
Therefore pre-emphasis may sound a daft thing to do but high
frequency sounds naturally occur at much lower levels and the
technique works very well if used correctly.
Keith Hayler
BBC Transmission.
John Gilliver
Keith Hayler (keith....@bbc.co.uk) wrote:
: The reason for the 'hissing' distortion being more noticeable
: technique called 'pre-emphasis'.
: Keith Hayler
: BBC Transmission.
What may make some difference - not sure which way - is that TV FM uses a
deviation of 50 kHz, and FM radio 75 (I think; going from memory here, not
GEC knowledge). Not sure if the pre-emphasis time constants are the same for
the two either (I know they're different for USA and European radio).
--
J. P. Gilliver | Tel: +44 1245 242133 | Usually NOT
GEC-Marconi Research Centre | Fax: +44 1245 242124 or 475244|writing for GEC!
GEC-Marconi Ltd, GREAT | Home: G6...@soft255.demon.co.uk, G6JPG@GB7NNA
BADDOW, Essex, CM2 8HN, UK. | Email: john.g...@gecm.com (-:!
Paul Ratcliffe
>I think this is due to the far greater bandwidth of the TV audio signal.
>VHF radio is 150 kHz while TV audio is 300 kHz, which means more 'room'
>for high signal peaks or high frequencies, both of which occur with
>'s-es'.
As I remember, the transmission specs. for analogue TV sound and VHF
radio are identical. Both use FM with a maximum deviation of 75kHz.
---
* PDQWK 2.5 #1
Richard Lamont
In article <84609999...@ld08-164.compuserve.com>,
Not quite true. There are several different transmissions standards
around the world, but generally PAL systems use 50 kHz peak deviation
and NTSC systems use 25 kHz.
--
Richard Lamont
ric...@stonix.demon.co.uk
http://www.stonix.demon.co.uk/
John Gilliver
Richard Lamont (ric...@stonix.demon.co.uk) wrote:
: In article <84609999...@ld08-164.compuserve.com>,
: Paul Ratcliffe <7063...@compuserve.com> writes:
[]
: > As I remember, the transmission specs. for analogue TV sound and VHF
: > radio are identical. Both use FM with a maximum deviation of 75kHz.
: Not quite true. There are several different transmissions standards
: around the world, but generally PAL systems use 50 kHz peak deviation
: and NTSC systems use 25 kHz.
[]
I'd remembered the 50 figure as well, with 75 for Band II. (I didn't know
about the NTSC lower deviation though.) The one thatI think _is_ identical is
the pre-emphasis time constant; I vaguely remember a figure of 75uS, and that
Band II radio (at least) in the USA used 50, thus meaning receivers for there
sounded wrong if used here and vice versa.
Richard Lamont
In article <54qcft$1...@miranda.gmrc.gecm.com>,
g6...@gmrc.gecm.com (John Gilliver) writes:
> The one that I think _is_ identical is
> the pre-emphasis time constant; I vaguely remember a figure of 75uS, and that
> Band II radio (at least) in the USA used 50, thus meaning receivers for there
> sounded wrong if used here and vice versa.
Wrong way round! We use 50 us, the USA uses 75 us.