Is temperature a factor when recording?

Hi. I'm placing this post in this "Creating sample sets / recording organs" category, but if it is more appropriate under "General" please feel free to move it.

Last Sunday while on vacation in San Diego, I attended an afternoon concert of the outdoor Spreckels Organ in Balboa Park. While I don't plan to record any organs, I was intrigued when the organist (Robert Plimpton) mentioned that he was limited to using stops in the medium to loud range during the heat of the afternoon. He said soft stops could not be heard well when it was hot. He mentioned that you can hear them in the early morning or at night, however. Is temperature a factor you take into account when recording pipes for sample sets? Just curious.

Also, I noticed that although the organ was outdoors and thus there were no walls to reflect sound, it was not completely dry. There seemed to be a small amount of reverberation. Perhaps about a 1/2 second, or less. Maybe all in my head. I purchased a CD recording of Plimpton playing some of the same selections that he played at the concert. The recording was disappointing to me. The same selections seemed to have no reverb at all on the CD and did not sound near as good as I heard at the actual concert. Perhaps it is a matter of microphone placement. Not sure. Any thoughts?

Regards,
Jon

Hi Jon,

The reverb was not in your head. I live in San Diego and have heard the Austin organ in the park many, many times. The reverb you heard was the organ bouncing off the museums behind the pavilion. The louder the organist plays the more you hear it.

Jeff

Hi. I'm placing this post in this "Creating sample sets / recording organs" category, but if it is more appropriate under "General" please feel free to move it.

Last Sunday while on vacation in San Diego, I attended an afternoon concert of the outdoor Spreckels Organ in Balboa Park. While I don't plan to record any organs, I was intrigued when the organist (Robert Plimpton) mentioned that he was limited to using stops in the medium to loud range during the heat of the afternoon. He said soft stops could not be heard well when it was hot. He mentioned that you can hear them in the early morning or at night, however. Is temperature a factor you take into account when recording pipes for sample sets? Just curious.

Also, I noticed that although the organ was outdoors and thus there were no walls to reflect sound, it was not completely dry. There seemed to be a small amount of reverberation. Perhaps about a 1/2 second, or less. Maybe all in my head. I purchased a CD recording of Plimpton playing some of the same selections that he played at the concert. The recording was disappointing to me. The same selections seemed to have no reverb at all on the CD and did not sound near as good as I heard at the actual concert. Perhaps it is a matter of microphone placement. Not sure. Any thoughts?

Regards,
Jon

Hi Jon.

Well, temperature will affect the density of air and hence the transmission of sound, but I doubt it is all that important when recording individual pipes, fairly close up. Temperature is far more of a factor when the recorded pipes need to be as close to 'in tune' as possible.

I'm sure others who are far more knowledgeable will have things to say.

Hello All,

I wish to expound on the notion of air temperature and tuning. My "other job" for nearly 30 years has been in the engineering field, and having earned advanced university degrees in engineering, combined with being born with absolute pitch, I am the person who is qualified to answer your questions on this topic.

In the above response, Alan correctly asserted that ambient temperature does change the pitch of pipe organs due to a change in the density of the air in the room enclosing the pipes. As the density of air decreases, the speed of sound in air also decreases, because less dense air contains longer mean distances between air molecules. This negative change in the speed of sound in air (or any other gaseous medium) shifts the resonant frequency upward. In the case of an organ pipe, a previously tuned pipe sounds sharp as the ambient air temperature increases, and the corresponding air density decreases. The effect is noticeable if one has the capability of comparing with a given starting pitch.

Anyone who has inhaled the gas from a helium-filled balloon, has had the laughable experience of hearing his/her voice sounding much much higher than usual. Why? Because, when one inhales helium (a gas of much less density than air), the vocal tract is filled with helium when the person exhales and speaks. The lowered density of helium, combined with an unchanged size and shape of one's vocal tract/sinus cavity, causes the voice to sound characteristically "Munchkin-like". Caution: do not inhale helium for too long a stretch of time. You will begin to suffocate, because the helium you inhale tends to displace the oxygen your lungs need to nourish the hemoglobin in your blood.

There is an opposite effect when one inhales a non-poisonous gas that is more dense than normal air, for example, Sulfur Hexaflouride (Chemical composition = SF with a subscript 6 where S stands for Sulfur, element #16 and F stands for element #9 in the periodic table of the elements). Although the name "gaseous sulfur hexaflouride" sounds formidable, it is actually chemically inert. It is also much more dense than air. Anyone who has had experience inhaling a few breaths of sulfur hexaflouride (a gas at room temperature), and speaking in a seemingly normal tone of voice, has experienced the opposite effect of inhaling helium -- that is to say, one's voice goes noticeably lower than usual.

When the ambient air temperature increases by more than about 6 degrees Celsius (about 10 degrees Fahrenheit) in temperature, the resonant frequency of pipes in a pipe organ becomes noticeably shifted upwards, at least to this listener who has absolute pitch. More than about 20 degrees Celsius (36 degrees Fahrenheit) results in pitch swings of approximately a quarter tone sharp (if the temperature goes up) or a quarter tone flat if the temperature goes cold.

While still in high school, I was first-chair trumpet player in the school's marching band. I can recall a bone-chilling day when marching at half time for a football game where the ambient temperature was approximately -5 degrees Fahrenheit (-20 degrees Celsius) and I could not bring my trumpet into tune. It was more than a semitone flat, despite my best efforts to push the trumpet's tuning slide in all the way.

Enough of my rambling. Hopefully this little discourse cleared up the notion of temperature versus pipe organ tuning for you.

Cheers,

Joe jcfelice88keys

Hello All,

I wish to expound on the notion of air temperature and tuning. My "other job" for nearly 30 years has been in the engineering field, and having earned advanced university degrees in engineering, combined with being born with absolute pitch, I am the person who is qualified to answer your questions on this topic......................
...................Enough of my rambling. Hopefully this little discourse cleared up the notion of temperature versus pipe organ tuning for you.

Cheers,

Joe jcfelice88keys

A valiant lecture, Joe. However, the question was not about tuning it was about temperature and loudness.

Another factor that affects sound is humidity. I can imagine that around daybreak the humidity is higher and this helps to bring out softer pipes.

Isn't it another issue?

I don't know how much respect the people in the park have for the organ playing. If not and if it's hot so many people will come to the park, the sound of softer stops will not be heared because all the noise of the crowd. With less people (chilly morning/nights) this effect is less.

Aside from temperature changing the pipe's pitch outdoors, the same holds true indoors, especially after playing for a length of time. Due to the accumulated heat in a pipe chamber with respect to unenclosed pipes I have heard variations (my theory) . I have noticed such differences in the past and was told it, too, was in my head or maybe the inconsistency of the organ tuner. (Too bad "we" sometimes listen with our "technical" ears).

Quite a few years ago, I made a recording of a church PO. On the previous day (before a scheduled concert) I recorded the organist's practice session. This church was very budget conscious and kept the heat quite low when the church was unoccupied. The pitch change was quite obvious, but so was a difference in volume. (The difference being noted was from the practise session to that of the concert). The mics and all reordiing equipment remained unchanged. The main reason for recording the practice session was to establish recording levels. At the time, I didn't correlate these changes to temperature, but the above post opened that thought process again.

Since large organs need time to be sampled, several days maybe, how much variation can be attributed to such physical changes or is that more or less overlooked?

By the same token, I am convinced that my Carver amps sound better after operating for a half hour or so. My friend tells me that's because the organist (me in this case) has had some practice time during that half hour. Or is this another thing in my head?

Rgds,'
Ed