The Physics of Sound at the Ballpark

Major League Baseball recently noted the 75^th anniversary of Lou Gehrig’s farewell speech. His words have become iconic because of their simple dignity in face of the grave misfortune befallen a man known for his personal strength and dedication – The Iron Horse.

I have always found added poignancy in the strong echoes emphasizing the word at the end of each pause. “Today-day, I consider myself-self, the luckiest man-an on the face of the Earth-rth.”

As the sounds at the park have changed from the organ airs of old to the rock and hip-hop of today, the echoes from the speakers seem to have also faded into the past. But before I speculate on the death of the echo, let’s examine the physics of sound at the ballpark.

Most of you know the old adage about lightning and thunder. For every five seconds between the flash and the sound, the lightening is one mile away. This works because the light travels as fast as anything possibly can. I can always remember the speed of light because it takes a billionth of a second to go past a ruler. In other words, the speed of light is about a billion feet every second or 186,000 miles per second.

So, the lightning flash reaches you almost instantly. However, the speed of sound is only a little over 1,000 feet per second. In five seconds it travels a bit more than 5,000 feet, or one mile. The time between the lightning and the thunder can then be used to find the distance to its source.

According to Baseball Almanac, the first public address system in a big league ballpark was used in New York on July 5^th, 1929 during a game between the Giants and the Pittsburgh Pirates. As a child I remember huge speakers placed out in center field – often in the batter’s eye. This was in the early sixties, not the thirties!

Sitting in the bleachers you would hear the sound directly from the speaker. A bit less than a second later, you would hear the echo as the sound returned to the cheap seats after bouncing off the stands behind the plate. The distance between my seats and the grandstand was about 500 feet.  Since the sound had to get there and back, it traveled about 1,000 feet, so it took about a second.

You can still hear these echoes in ballparks today, but mostly during batting practice when the park is relatively empty and the PA system gives you a moment of quiet. The crack of the bat echoes throughout the yard. However, once the game is going there seem to be no echoes produced by the sound system.

There are interesting implications of the speed of sound for a great running outfield catch. So often the announcer will describe the fielder as “taking off at the crack of the bat.” The physics of the matter makes this simply impossible.

Just like the lightning and thunder, the fielder sees the batter hit the ball almost instantly because the speed of light is so very high.  However, an outfielder is over 300 feet away, so it will take about one-third of a second for the sound to reach him. By that time, he better already be moving toward the ball. Indeed, StatCast data seem to confirm that most fielders are in motion within a third of a second.

It always helps to have some actual opinions to match that data, however, so we put the question to some of the outfielders on the Giants and A’s. Well, three questions, actually:

1. Do you hear the crack of the bat before, during, or after you see the ball hit the bat?
2. Do you begin moving toward the ball before or after you hear the crack of the bat?
3. How does the crack of the bat influence your route to the ball?

Gregor Blanco of the Giants agrees that he hears the crack of the bat after he sees the ball hit it, and felt it definitely helped him with his route. Sam Fuld of the A’s concurs, “Reality. Absolutely use it. It’s not a conscious thing, but it’s absolutely usable…It’s all instinctual, but if I hear good contact, I’m naturally going to break backwards. Especially on the corners, if you see a full swing and you can’t tell if he got all of it or not, the sound can help.”

San Francisco’s Angel Pagan has a different point of view. “I never go by the crack of the bat, sometimes [the crowd is] so loud you can’t hear it. You have to go by instincts.”  Blanco concurred, especially when it comes to going from park to park. “Sometimes, the crowd is really loud and you can’t hear it. In some parks, you are able to hear it [and it] can let you know how good that person hit the ball. You can’t always hear it in San Francisco.”  Fuld thirded that motion. “Yeah, I have noticed it’s different. Especially in Tampa, the crack of bat is as loud as it’s going to get. No crowd, the roof’s there. Ben Zobrist talked about playing the outfield in Oakland, and it’s hard to hear the ball. The crowd is part of it, but [there’s] something to the air quality as well. [It’s] easier to hear in any place that’s closed.”

Blanco also commented on echoes, “Good ballparks to hear the echo are Arizona, Milwaukee, because the roof is closed and you can hear it in the outfield.”

That’s not to say everyone takes advantage of these echoes. “I just use the trajectory,” says Giants outfielder Justin Maxwell. His teammate, Hunter Pence kind of sums it up, “I don’t really know. I don’t know. I think you do use it subconsciously, and you don’t even realize it…Subconsciously you do it, but you don’t consciously use the crack of the bat.”

So where does that leave us. Unfortunately, still speculating about the demise of echoes during the game in today’s ballparks. Don’t worry, I have an explanation for you – let me know if you have a better one.

In most (all?) parks, the gigantic set of speakers in center field has been replaced by hundreds of smaller speakers placed around the park. Since there are so many smaller speakers around, each one can have a lower volume then a single set in center. The smaller speakers at lower volume aren’t loud enough to create any noticeable echoes.

You may not realize this, but the electrical signal sent to all of these speakers travels at nearly the speed of light. So, the sound comes out of all the speakers everywhere in the park at essentially the same time. All the fans hear the same hip-hop beat at the identical instant with no echo.

Makes sense, doesn’t it? Am I correct? Well, I’ll have to go with Hunter Pence on this one – “I don’t really know. I don’t know. I think…”

References & Resources

• Special thanks to Eno Sarris for interviewing the players and transcribing their quotes.