[Gray_Wolf]

On 5/9/2016 8:03 AM, Frank Stearns wrote:
Trevor writes:

On 9/05/2016 2:11 PM, PStamler wrote: On Sunday, May 8, 2016 at 12:14:03 PM
UTC-5, Peter Larsen wrote: Speed of sound changes with pressure and thus one
some days the dimensions of the instrument may be slightly more suitable for
your preferred intonation. I also think I remember that relative humidity
makes a difference. According to several online references, the speed of sound
changes with temperature and relative humidity, but not with atmospheric pressure.

AFAIK it changes with air density, which is dependent on both pressure
and temperature.

Long, long ago, I did outdoor PA at a world's fair for six months. Our venue did a
new 30 minute act on the hour every hour from 10:00 am to 10:00 pm. We did split
shifts, I did the evening shows, a friend did the morning shows. On any typical day
we'd see a 30-40 degree temp swing across that time, with perhaps a similar
percentage swing in Rh (mid-high desert, so there could be a fairly large Rh swing
across the day; this is unlike the USA mid-west/East where often the Rh is high and
stays high through the course of a day).

We'd each swear that the other guy was a deaf doofus as we'd see the EQ settings
left over from one evening to the next morning. He was cutting top and adding bottom
(very simple console with only HF and LF controls), and I would wind up with much
the exact opposite.

Then we each had the opportunity to cover for one another, taking a double shift on
those days and working the full 12 hours worth of shows. Sure enough, through the
day, the EQ would creep around to sometimes dramatic extremes as the temp and Rh
changed.

As time went by and I also mixed other shows there with better gear after the fair
had closed but the venue was still in use, I discovered that by far the best sound
was early evening, just after dark, when the Rh went up and the temp had cooled to
some 60-65 degrees. If fact, it often sounded amazing at that time.

But at high noon in the dry heat of the day, things typically sounded awful. (And
poorly conditioned control rooms can have similar issues.)


The state of the air can make a large difference in sonics.

Frank
Mobile Audio

Frank, I experienced the same thing in my shop in Nashville.
I had friends that would come by and we'd jam after hours.
It was very noticeable in winter. The heater would cycle between
almost too hot and almost too cold. You'd notice a lot of change
in a very short time. Cooler is better.