## Pi Day, 2011 (with Music)

Every year, we at CatSynth join numerous other mathematics enthusiasts, geeks and otherwise eccentric characters in celebrating **Pi Day** on March 14.

March 14 is notated in the U.S. and some other countries as “3-14″, which evokes the opening digits of π (pi). Although the date representation is a very arbitrary connection to the number, we also recognize that the representation of π in decimal digits is arbitrary, an accident of human beings having ten fingers. So this year we are exploring the representations in binary and other related bases.

To represent an integer in binary, one of course presents it as a sum of powers of two, e.g., **11 = 8 + 2 + 1** or **1011** in binary. But one can also represent fractional numbers in binary. Digits to the right of the decimal point represents powers of one-half. So the binary number **0.11** is **1/2 + 1/4**, or **3/4**. Fractions like **1/3** can be represented with repeating digits as **0.010101…**, much like in base ten. And this concept can be extended to irrational numbers like π.

The author of this website has calculated 32768 digits of pi in binary. We reprint the first 258 below:

11. 00100100 00111111 01101010 10001000 10000101 10100011 00001000 11010011 00010011 00011001 10001010 00101110 00000011 01110000 01110011 01000100 10100100 00001001 00111000 00100010 00101001 10011111 00110001 11010000 00001000 00101110 11111010 10011000 11101100 01001110 01101100 10001001

The initial “11″ represents the 3 in π, and the remaining digits begin the non-integral portion. Like in the decimal representation, the binary representation continues forever with no particular pattern. While not as iconic or memorable as the decimal representation 3.14159…, there is something about the binary representation that makes it seem more universal, i.e., based on fundamental mathematical truths rather than a quirk of human anatomy. For me, the binary representation also lends itself to musical ideas. And for the occasion, I have created a couple of short synthesized pieces representing the 32768 binary digits of pi. In the first example, each binary digit represents a sample. The “1″ represents full amplitude and the zero represents no amplitude (silence). The result, which at 44.1kHz sample rate is less than one second long, can be heard below.

The random configuration of digits sounds like noise, and more specifically like white noise, suggesting something approaching uniform randomness at least to human hearing. I also made an example slowed down to a level whether the individual samples became musical events. I find this one quite interesting.

With some additional refinement (and may some more digits to extend the length), it could certainly stand alone as a composition.

One interesting counterpoint to the notion that digits of pi form white noise is a conjecture related to its representation in hexadecimal (base 16), which as a power of two is “closer” to binary and seemingly less arbitrary than decimal. From Wolfram MathWorld, we find the following “remarkable recursive formula conjectured to give the *n*th hexadecimal digit of π – 3 is given by where is the floor function:

The formula is attributed to (Borwein and Bailey 2003, Ch. 4; Bailey et al. 2007, pp. 22-23). If true, it would add some sense of order to the digits, and thus additional musical possibilities.