Archive for December, 2009

Holiday Donations

Friday, December 18th, 2009

by Alison Moore

The holiday season is here (back again so soon, it seems!).

Here in New England, cold (read VERY COLD) weather has also arrived. We held our annual Yankee Swap here in our Burlington, MA office yesterday.  Always a fun event- with a variety of delicious treats that encourage me to get on my elliptical machine at home in the evening. It’s not worth the guilt to skip my workout.

By the way, the most popular gift was the DVD player – where did someone find that for our $10-$15 price range? Must have been a Black Friday shopper. The most surprising gift was a fish bowl set-up…including a fish of course (yes a live Betta fish).

So, if the cold weather must come, we can’t stop it, but we can still enjoy our holiday fun! Many of us also remind ourselves how fortunate we are this time of year. Others give attention- volunteering, donations- to supporting others who may be experiencing tougher times.

In an effort to also offer support, HMMH has contributed to two organizations who are focused on caring for people who are experiencing economic difficulties. We are proud to share that we have contributed to each of these organizations in past years as well, recognizing the value they offer to a individuals and families in need. It is also important to HMMH that they are each involved in communities in close proximity to each of our office locations- Burlington, MA, Sacramento, CA, Richmond, VA and Washington DC.

The two organizations to whom we have made a holiday donation are Feeding America and the Citizens Energy Oil Heat Program.

A bit about each of these organizations:

  • People in every community face the risk of going hungry. For every $1 donated, Feeding America helps provide 7 meals to men, women and children facing hunger in our country. Feeding America works with large corporate donors to secure food and grocery products on a national level to distribute, to local food banks. The relationship that the Feeding America organization builds with larger corporations also helps facilitate a relationship between a local food bank and local grocery store, for example.
  • Many families need assistance to stay warm and safe. The Citizens Energy Oil Heat Program works with thousands of oil heat dealers and has delivered millions of gallons of discount home heating oil to poor and elderly households since 1979.  This program helps protect needy families from volatile heating oil prices, which often leave households having to choose between heating the home and paying for other life essentials, such as food, health care, or clothing.

Happy Holidays!

That Crackly Sound

Friday, December 18th, 2009

by Doug Barrett

Four more days to go until the longest night of the year and it’s starting to get cold here in New England!  Last night’s low was around 14 degrees F. in Boston, and last weekend, up in New Hampshire, it was colder still.  My fabulous spouse and I live about five miles from Boston’s Logan International Airport, and depending on which way the wind is blowing, sometimes we are treated to a steady stream of departing aircraft.  The other day, after a particularly cold morning, she asked why the aircraft sound different in cold weather – both louder and “crackly” as she put it.

The short answer is that it’s complicated.  As for the long answer, I suspect that she’s noticing the dependence of atmospheric absorption of sound on temperature and relative humidity.  Leo Beranek said it better than I could: “energy is extracted from a sound wave by rotational and vibration relaxation of the oxygen molecules in the air.  The vapor content of the air determines the time constant of the vibration relaxation… In addition, this ‘molecular absorption’ depends in a major way on temperature.” (Leo L. Beranek, Noise and Vibration Control, McGraw Hill, 1971, P.170)

It’s especially interesting that at any particular relative humidity, molecular absorption peaks at a given temperature.  In other words, one can’t simply make a generalization that sound “travels” better when it’s cold outside.  Adding to the complexity, the effects of temperature and humidity vary dramatically depending upon the frequency of the sound.  In general, wider variations exist at higher frequencies.  Notice on the first figure below (reproduced from Beranek) that there is relatively little sensitivity to temperature or humidity at 500 Hz – only about 3 dB per 1,000 feet across a temperature range of 100 degrees F.  In contrast, at 8 kHZ, the second figure shows a whopping variation of up to 50 dB per 1,000 feet over the same temperature range.

Atmospheric Absorption for aircraft-to-ground propagation (500 Hz, 1,000 Hz, 2,000 Hz)

Atmospheric Absorption for aircraft-to-ground propagation (500 Hz, 1,000 Hz, 2,000 Hz)

Atmospheric Absorption for aircraft-to-ground propagation (8,000 Hz)

Atmospheric Absorption for aircraft-to-ground propagation (8,000 Hz)

Regarding the “crackly” sound, here are some molecular absorption values that I pulled from the figures: At 500 Hz to 1 kHZ (approximately speech frequencies), one expects molecular absorption at a rate of about 1 to 2 dB per 1,000 feet of propagation on either a pleasant summer morning (60 degrees F. and 50% RH) or on a nippy winter morning (10 degrees F. and 20% RH).  That is to say, at lower to mid-range frequencies, there’s not a big seasonal difference.  At 8 kHZ, however, one expects absorption at a rate of about 20 dB per 1,000 feet with the summer conditions, but only about 6 dB per 1,000 feet with the winter conditions.  Less high-frequency absorption with cold, dry weather equals more “crackly” sounding!

The Caveman Theory

Thursday, December 10th, 2009

by Mary Ellen Eagan

I hate it when my husband is right.  When our daughter Molly was an infant (and colicky), she rarely slept more than 2 hours at a time.  One day, a friend asked if she was sleeping through the night, and David immediately responded, “Sure.”  “What?!” I said, incredulously.  Thus began my interest in not only understanding awakenings from aircraft noise, but awakenings from crying babies.

David had an instant, easy explanation: evolution.  His basic premise was that in prehistoric times, women stayed up with babies at night so that men could be “on their game” to hunt mastodon in the morning.  Well, now there’s apparently some scientific evidence that buzzing flies are more likely to wake men than crying babies.

I guess I should stop wishing for the toilet seat to be down, huh?

But seriously, this does make me wonder if there are gender differences in awakenings from aircraft noise.  I’ve never heard of it, and assume the analysis has been done, but haven’t seen much written on the subject.  I’ll report back after this week’s FAA Noise Research Roadmap, which will be talking about awakenings.

Proposed Air Quality Standards for Sulfur Dioxide

Wednesday, December 9th, 2009

by Phil DeVita

For the first time since 1971, the Environmental Protection Agency (EPA) has proposed to revise the National Ambient Air Quality Standards for sulfur dioxide (SO2).  The proposal calls for a new 1-hour standard.  The current SO2 standard consists of a primary 24-hour and annual standard.  There is also a secondary 3-hour standard.  The primary standards were set to protect the public health including the health of the sensitive population (e.g. asthmatics, children, and the elderly).  The secondary standard was established to address public welfare and the environment.  Recent health studies have linked short-term (e.g. ranging from 5 minutes to 24-hours) SO2 exposures to adverse respiratory effects including increased asthma symptoms and bronchoconstriction.

The EPA is currently taking comments on the new 1-hour standard ranging from 50 and 100 parts per billion (ppb).  Since the revised standard would be more protective, the EPA is proposing to revoke the current 24-hour and annual standard.  The current proposal only addresses the primary standards.  EPA will address the secondary standard (e.g. 3-hour) under a second proposal in 2011.  The current and proposed SO2 standards are presented in the following tables.

Current Standards

Averaging Time

Primary Standards

Secondary Standards

3-Hour

none

500 ppb

24-Hour

140 ppb

none

Annual

30 ppb

none

Proposed Standards

Averaging Time

Primary Standards

Secondary Standards

1-Hour

(50 to 100 ppb)

none

3-Hour

none

500 ppb

24-Hour

Revoke

none

Annual

Revoke

None

EPA is also proposing changes to the monitoring requirements for SO2.  Monitors would be placed in urban areas and areas with high SO2 emission levels.  The proposal includes changing the Air Quality Index (AQI) to reflect the new standards thereby improving states’ abilities to alert the public when short-term levels may affect their health.

The public comment period is open for 60 days after the proposal is published in the Federal Register.  EPA will hold a public hearing on January 5, 2010 in Atlanta.   EPA must issue a final decision by June 2, 2010.

The proposed SO2 revision comes off the heels of EPA’s recent proposal to revise the nitrogen dioxide (NO2) standard.  EPA is proposing to include a new 1-hour NO2 standard ranging from 80-100 ppb while also soliciting comments as low as 65 ppb and  up to 150 ppb.  The proposal would retain the current annual standard of 53 ppb.  The comment period has closed on the NO2 standard and EPA must issue a final decision by January 22, 2010.

These proposed standards will affect all types of emission sources, including aviation.  For areas in non-attainment and maintenance regions, general conformity determinations will need to demonstrate that project emissions will not exceed these standards prior to FAA approving federal funding.