Blog logo, you're not missing much
AudioAcoustics

Serving the Acoustics Community Since 1994

Cross-Spectrum Acoustics Inc. offers Sound & Vibration Consulting Services

June
Sun Mon Tue Wed Thu Fri Sat
     
   









Jun 18, 2005

HMMH’s Chris Bajdek wrote an article for North American Windpower magazine on noise issues of wind power facilities:

Although wind turbines are quieter than they were 25 years ago, affected communities may not accept the argument that turbine noise is covered up (masked) by the wind. And while it may be demonstrated that a proposed wind farm will not exceed regulatory noise limits, facility noise may be sufficient to cause adverse community reaction once the wind farm goes online.

There’s also some good info the article about community reaction (annoyance) to wind farm noise and low-frequency issues.

Low-frequency noise in particular is often cited as a major concern by community activists because physical ailments (nausea, dizziness, stress, anxiety, etc) have been attributed to the low-frequency noise from wind turbines. However some research has shown that these ailments may be caused by the “shadow flicker” of the rotating turbine blades - that’s not to say that these health effects aren’t real, it’s just that the source may be visual rather than aural.

[Tag: ]


permanent link

 

Several news outlets have picked up an AP article titled “Cops Raid Wrong Duplex With Noise Device” where the “noise device” in question was a flashbang grenade.

I have a bit of a problem with the characterization of a flashbang grenade as a “noisemaking device” - it’s a basically an explosive device! It’s like calling a cell phone a “radio frequency” device. Yeah, it’s true, but totally misses the point.

(Of course the real issue isn’t the use of a noisemaking device, it’s the fact that the cops raided the wrong house! But I’ll leave that issue to the more political blogs)


permanent link

 

Jun 16, 2005

NPR’s Day to Day ran a feature on Sonare Technologies’ Babble voice privacy device (which, contrary to some beliefs), does not involve sound cancellation techniques.

The NPR talks about Sonare’s philosophy of “sound as an element of design.” It’s a philosophy worthy of debate. Absorbing and blocking sound can be expensive, and as the NPR feature notes, we as humans do need some sort of aural stimulus (spend time in an anechoic or very quiet environment and you’ll see what I mean). But Babble resolves privacy issues by increasing sound levels, just like a masking system. Is this a good thing?


permanent link

 

Wired News: Sagging Radio Plays Digital Card

“Radio knows that it needs to make that jump to the digital universe,” said Tom Taylor, editor of the daily newsletter Inside Radio, which is published by a division of Clear Channel Communications. “Radio sees it as a journey it has to make to reach continued growth and viability, and a chance to have additional stations, serve listeners and make more money.”

This is a timely article, given the recent BAS presentation on digital radio at WFCR at UMass Amherst. Charles Dubé and Richard Malawista shared their experiences with digital radio at WFCR and the discussion was enlightening. One thing they pointed out was that the big radio conglomerates were embracing digital radio because they are hoping that the world “digital” would help stem their ratings slide - of course these conglomerates apparently don’t think that commercial radio’s limited playlist (which basically consists of “50 Cent”, “NORE”, “Eminem”, “More 50 Cent”, “Christina Aguilera”, “Repeat 50 times”) has anything to do with the declining audience. Sigh.

One thing we were told during the presentation was that some in the digital radio industry need to downplay the expectations of CD-quality from digital radio since, at 96 kbs and 15 kHz bandwidth, iBiquity’s HD Radio is nowhere near CD-quality (but it still sounds better than analog FM). Apparently not everyone got the message. From the article:

“FM is going to sound like CDs, and AM will sound like today’s FM,” Struble said. “You’ll eliminate the static and hiss and pops, which will become a thing of the past because of digital processing.”

You’ve got to love marketing. At least DRM isn’t part of the HD Radio spec (but I forgot to ask about “broadcast flag”-type copy control).

The audio stream uses an AAC-based lossy compression. Because we are talking about audio streams, HD-Radio’s will have to ‘buffer’ their streams for a few seconds before playing digital audio, just like we see with Real Audio/WMA streaming audio in web browsers. HD Radio stations will compensate for this by playing normal analog radio when you first tune to a station. When the radio has buffered enough data, the radio will switch to digital audio. The buffered audio has another downside - because of the buffering delay, digital audio won’t be real time. When you NPR station announces that it’s 8:00am, the time will really be 8:00:08am. The analog feed will also be used as a fall-back signal in case the digital signal gets too weak (at the edge of the broadcast area for instance).

Because we’re talking about radio, we still have to deal with added audio compression. Theoretically HD Radio could transmit raw audio without compression, but that would lead to frustration for listeners in cars or in noise-sensitive environment. One BAS member made a suggestion that HD should transmit the raw feed with a subchannel containing compression instructions, and then let the client radio perform the (optional) compression. I love this idea, but given that the format is fixed, it’s not gonna happen.

I’m also disappointed that the maximum bit-rate is fixed at 96 kbs. From what I understand, this value was chosen because a) higher bitrates might interfere with analog FM channels, and b) listening tests showed that 96 kbs was “good enough.” I would have preferred to see a much higher maximum bit-rate (perhaps 320 kbs), with an interim limit of 96 kbs. That way, there is an option to increase the bit rate in the future. With the current U.S. HD Radio format, we can’t do that without revamping the format (and buying new transmission equipment and radio receivers). Oh Well.

But all in all, HD Radio is a good thing. I especially like the subchannel option which will hopefully give us some additional entertainment and informational listening options.

[Tag: ]


permanent link

 

Struggling DC-3 had prompted complaints from residents near airport: “They say the DC-3 cargo plane that routinely flew over their Fort Lauderdale neighborhood often was too low, too loud, too labored.”

In trying to convince potential clients that noise analyses could help detect mechanical problems and reduce maintenance costs, a former boss of mine used this axiom: “if you can hear it, it’s costing you money.”

Maybe they saying should be “if you can hear it, it might kill you.”


permanent link

 

The BBC is offering free downloads BBC Philharmonic performances of Beethoven pieces.

I wish they had told me this before… At least I can look forward to downloading Symphony 6 and 9 in the future.


permanent link

 

Some people have way too much time on their hands.


permanent link

 

Jun 13, 2005

SoffitTraps from RealTraps: in-room low-frequency absorption that actually looks good.


permanent link

 

The big news last week was the announcement that Boston Acoustics is being acquired by D&M Holdings, parent company of Denon and Marantz.

Acquisitions are sometimes known to, well, negatively affect products. Given the quality of the Denon and Marantz product lines (can you tell I’m a big fan?), I think Boston Acoustics is in good hands.

Besides, Andy deserves his payday.


permanent link

 

While I wasn’t paying attention, the Noise Pollution Clearinghouse has been busy: Quiet Classrooms is a resource for parents, educators, administrators and architects to help create quiet learning environments. Good info.


permanent link

 

Jun 03, 2005

India’s rapid growth brings community noise problems. One Acoustician in Bangalore offers some tips (alternate link) on reducing the noise:

The mistaken impression is that an acoustics expert is required only for special venues like cinemas, auditoria and studios. This is a myth. To realise the true potential of any built space the second sense of humankind - hearing - must be given its due importance.

..

Discotheques, pubs and nightclubs are sources of heavy doses of low-frequency soundwaves that are the most difficult to control. They have large wavelengths and need massive surfaces to control them.

..

The design community tends to confuse sound absorption and noise isolation. You require a porous material to absorb sound. Quite conversely, a porous material does not block noise.

..

Architects need to go back to the module on acoustics taught in architectural/civil courses or call in an acoustics expert.

This is good stuff. I might have to steal it.

..

(I’m kidding, please don’t sue me.)

[Tag: ]


permanent link

 

Wall Street Journal: Sounds of Silencers Are Loud and Clear: PCs Are Too Noisy

Tomas Risberg, a Stockholm neurologist, calls computer noise “a freedom issue.” Why “should I have to listen to something I don’t want to listen to?” demands Dr. Risberg, who helped persuade the Swedish government to adopt computer-noise standards.

[via Boing Boing]


permanent link

 

United States of Noooooo!: it might not make sense if you haven’t already seen a certain summer blockbuster.


permanent link

 

ABC News: Aircraft noise may impair kids’ mental development - informative, but then again, we already knew this.


permanent link

 

Jun 01, 2005

Random link of the day: Lucent Technologies’ (nee Bell Labs) anechoic chamber.

[Tag: ]


permanent link