What prevents FM radio from reaching CD quality?

[CurvKyle]

I've got a few assumptions such as noise or signal loss, but I don't know the real answer. Anyone know?

[whap2005]

Nothing. The reason current FM is of low quality is because it's analog and not digital. There is a new radio format called "HD Radio" that just came out that is actually better then CD quality. It will allow stations to transmit up to 3 different channels of HD sound on 1 frequency using compression technology. There is also an AM version of HD Radio that will allow better then CD quality sound over AM (We will finally start hearing music over AM again!). We will start seeing HD Radios becoming more popular in the next few years. (It also means the death of XM and Sirius which currently have less then CD quality sound and monthly subscriptions so if you own stock in either, you better sell it now)

[bascule]

I'm surprised the FCC doesn't try to deprecate AM radio and reclaim the frequency space for technologies that aren't such horrible bandwidth hogs, especially in the lower kilohertz bands which propagate so well and would be so useful for other purposes if just used with a different modulation technique.

[whap2005]

'IMPEACH BUSH: A global disaster, a national disgrace"

 

Unfortunately that's not going to happen. And even if it could happen, you would just have old Dick running the show so is that really a big improvement? (And this coming from a Moderate Repub...).

[Externet]

Hi. I like your question. Perhaps because I can answer.

 

The difference from FM broadcast and CD is barely audible if you can hear over 15 KHz, which I doubt unless you are 10 years old... If you disagree, do not argue and get a hearing test first; then we can discuss the subject.

 

The Federal Communications Commission FCC sets 15 KHz as maximum frequency response for a 200KHz channel bandwidth for FM stereo stations to avoid interference with adjacent channels and limits spurious emissions from overmodulation.

 

There is many CD recordings that are much worse than FM broadcasting, and there is many radio stations that sound much worse than a CD.

There is NO norm. And beyond, there is millions of ears each with a different opinion about what sounds better.

 

Radio stations do use audio processing to make their signal louder by compression and other effects to gain dial market competitivity, deviating from flat and realistic audio reproduction.

CDs are too often also recorded with coloration and effects to suit producers demands, disrespecting fidelity in an attempt to make more $ by leaning towards trendy sounds.

 

So, you can't cut all cheeses with the same knife.

 

ALWAYS remember the definition of distortion: Any and all difference from the original sound source. Don't tell me that singer XYZ sounds in front of you the same as in its tricked, equalized CD recording.

 

Miguel

Audio-recording engineer

-13 years working on audio processing equipment for broadcasting-

[CurvKyle]

I took one of those online hearing tests and I could hear up to 24hz. I'm 21 years old.

 

I've lived all over the country and the FM radio is definitely no comparison to my cd player. Some stations do sound better then others, but I can notice the difference.

[herme3]

The reason current FM is of low quality...

 

FM is low quality? Perhaps it depends on the radio station you listen to, but the station I listen to has very good quality. The only bad part is how they try to automatically balance the volume of the music. I mean, the volume is automatically reduced during the louder parts of the song. If the singer starts singing in a softer voice, the volume will automatically increase.

 

Do all radio stations do this? The station I listen to is very popular with stores and businesses, which might explain why they try to balance the volume. I doubt people would want to hear a sudden loud part of a song while they are working.

[Externet]

Truly, envious congratulations CurvKyle on your hearing abilities; but I believe you failed. How do you know the speakers you used for the 'online' hearing test are capable of "24Hz" ? Did you make a mistake meaning 24KHz? Well, 24 Hz is not bad either.

 

herme3:

Mostly yes, about 97% of radio stations do it in varied amounts. It is compression, limiting, clipping, multi audio-band equalizing, etc. Soft sounds are pushed up to FCC limits bringing a steady level with little dynamic range (difference between soft passages and loud ones) of about only 7 to 10 decibels.

A recognizable extreme example is watching a TV movie, were dialog is at nearly the same level of guns shooting. Yes, sure:rolleyes: . Convincing to those who have never heard a real shot.

Of course if the TV speaker was to reproduce the sound level of a shot, it would vomit its guts out at the first .22 cal firing.

 

The specialized audio processing equipment is at: http://www.orban.com. There is some instructive audio articles worth reading, but you have to dig for them at the site.

Edit- added : the document is titled "Audio quality in the FM plant"

Miguel

[bascule]

The difference from FM broadcast and CD is barely audible if you can hear over 15 KHz, which I doubt unless you are 10 years old... If you disagree, do not argue and get a hearing test first; then we can discuss the subject.

 

I can hear upwards of 19 kHz, thanks.

 

There is many CD recordings that are much worse than FM broadcasting, and there is many radio stations that sound much worse than a CD.

There is NO norm.

 

The norm is: FM radio is subject to interference, and without an immensely powerful transmitter with lots of elevation, that interference is going to rear its ugly head.

 

Radio stations do use audio processing to make their signal louder by compression and other effects to gain dial market competitivity, deviating from flat and realistic audio reproduction.

 

FM also comes nowhere close to a CD's 90dB of dynamic range, not that most people are listening to music which even comes close to using that, instead opting to listen to overcompressed pop shit.

 

ALWAYS remember the definition of distortion: Any and all difference from the original sound source.

 

Compare the signal paths:

 

CD -> DAC -> amplifier -> speakers

 

to:

 

CD -> DAC -> amplifier -> compressor -> FM transmitter -> antenna -> electromagnetic radiation -> antenna -> FM receiver -> amplifier -> speakers

 

FM has a lower frequency response, lower dynamic range, and introduces distortion. I think it's fair to say it sounds "worse than a CD"

 

I guess this is all moot considering I don't listen to the radio anymore. It sucks, but more for programming and ads than audio quality.

[CurvKyle]

Truly, envious congratulations CurvKyle on your hearing abilities; but I believe you failed. How do you know the speakers you used for the 'online' hearing test are capable of "24Hz" ? Did you make a mistake meaning 24KHz? Well, 24 Hz is not bad either.

 

yea 24khz, I'm not sure if my headphones were capable, but I could hear the high pitched sound when I click the button so I would assume they could.