I downloaded sample - hello.speaker.45 from class page.I cut with CNC milling machine and soledered some components.

and wrote this sample program.

        //
        // hello.speaker.45.c
        //
        // speaker PWM hello-world
        //    square wave, pseudo-random frequency
        //
        // Neil Gershenfeld
        // 11/14/10
        //
        // (c) Massachusetts Institute of Technology 2010
        // This work may be reproduced, modified, distributed,
        // performed, and displayed for any purpose. Copyright is
        // retained and must be preserved. The work is provided
        // as is; no warranty is provided, and users accept all 
        // liability.
        //

        #include 
        #include 

        #define output(directions,pin) (directions |= pin) // set port direction for output
        #define set(port,pin) (port |= pin) // set port pin
        #define clear(port,pin) (port &= (~pin)) // clear port pin
        #define pin_test(pins,pin) (pins & pin) // test for port pin
        #define bit_test(byte,bit) (byte & (1 << bit)) // test for bit set

        #define cycle_delay() _delay_us(2) // cycle delay
        #define current 150 // PWM current
        #define off 255 // PWM off

        #define MOSFET_pin (1 << PB1)
        #define MOSFET_port PORTB
        #define MOSFET_direction DDRB

        int main(void) {
           //
           // main
           //
           static uint16_t cycle,cycles,delay,bit,lfsr;
           //
           // set clock divider to /1
           //
           CLKPR = (1 << CLKPCE);
           CLKPR = (0 << CLKPS3) | (0 << CLKPS2) | (0 << CLKPS1) | (0 << CLKPS0);
           //
           //
           //
           TCCR0A = ((1 << COM0B0) | (1 << COM0B1) | (1 << WGM01) | (1 << WGM00)); // set OC0B on compare match and set fast PWM mode, 0xFF TOP
           TCCR0B = (1 << CS00); // set timer 0 prescalar to 1
           //
           // initialize MOSFET pin
           //
           clear(MOSFET_port, MOSFET_pin);
           output(MOSFET_direction, MOSFET_pin);
           //
           // initialize LFSR
           //
           lfsr = 1;
           //
           // main loop
           //
           while (1) {
              //
              // update 11 bit LFSR
              //
              bit  = ((lfsr >> 0) ^ (lfsr >> 9)) & 1;
              lfsr =  (lfsr >> 1) | (bit << 10);
              //
              // loop over cycles
              //
              cycles = (1 << 15) / lfsr;
              for (cycle = 0; cycle < cycles; ++cycle) {
                 //
                 // set PWM current on and delay
                 //
                 OCR0B = current;
                 for (delay = 0; delay < lfsr; ++delay)
                    cycle_delay();
                 //
                 // set PWM current off and delay
                 //
                 OCR0B = off;
                 for (delay = 0; delay < lfsr; ++delay)
                    cycle_delay();
                 }
              }
           }
	

and Worked!