Please copy the code into your empty sketch and compile and upload.

2.4 KHz and 8-9% duty cycle

void setup()
{
pinMode(3, OUTPUT);
pinMode(4, OUTPUT);
pinMode(5, OUTPUT);
pinMode(6, OUTPUT);
pinMode(7, OUTPUT);
pinMode(8, OUTPUT);
pinMode(9, OUTPUT);
pinMode(10, OUTPUT);
}

void loop()
{
digitalWrite(3, HIGH);
delayMicroseconds(25); // Approximately 10% duty cycle @ 2.6KHz
digitalWrite(3, LOW);
delayMicroseconds(10);
digitalWrite(4, HIGH);
delayMicroseconds(25); // Approximately 10% duty cycle @ 2.6KHz
digitalWrite(4, LOW);
delayMicroseconds(10);
digitalWrite(5, HIGH);
delayMicroseconds(25); // Approximately 10% duty cycle @ 2.6KHz
digitalWrite(5, LOW);
delayMicroseconds(10);
digitalWrite(6, HIGH);
delayMicroseconds(25); // Approximately 10% duty cycle @ 2.6KHz
digitalWrite(6, LOW);
delayMicroseconds(10);
digitalWrite(7, HIGH);
delayMicroseconds(25); // Approximately 10% duty cycle @ 2.6KHz
digitalWrite(7, LOW);
delayMicroseconds(10);
digitalWrite(8, HIGH);
delayMicroseconds(25); // Approximately 10% duty cycle @ 2.6KHz
digitalWrite(8, LOW);
delayMicroseconds(10);
digitalWrite(9, HIGH);
delayMicroseconds(25); // Approximately 10% duty cycle @ 2.6KHz
digitalWrite(9, LOW);
delayMicroseconds(10);
digitalWrite(10, HIGH);
delayMicroseconds(25); // Approximately 10% duty cycle @ 2.6KHz
digitalWrite(10, LOW);
delayMicroseconds(10);
}

765 Hz and 8-9% duty cycle.

void setup()
{
pinMode(3, OUTPUT);
pinMode(4, OUTPUT);
pinMode(5, OUTPUT);
pinMode(6, OUTPUT);
pinMode(7, OUTPUT);
pinMode(8, OUTPUT);
pinMode(9, OUTPUT);
pinMode(10, OUTPUT);
}

void loop()
{
digitalWrite(3, HIGH);
delayMicroseconds(100); // Approximately 10% duty cycle @ 765 Hz
digitalWrite(3, LOW);
delayMicroseconds(50);
digitalWrite(4, HIGH);
delayMicroseconds(100); // Approximately 10% duty cycle @ 765 Hz
digitalWrite(4, LOW);
delayMicroseconds(50);
digitalWrite(5, HIGH);
delayMicroseconds(100); // Approximately 10% duty cycle @ 765 Hz
digitalWrite(5, LOW);
delayMicroseconds(50);
digitalWrite(6, HIGH);
delayMicroseconds(100); // Approximately 10% duty cycle @ 765 Hz
digitalWrite(6, LOW);
delayMicroseconds(50);
digitalWrite(7, HIGH);
delayMicroseconds(100); // Approximately 10% duty cycle @ 765 Hz
digitalWrite(7, LOW);
delayMicroseconds(50);
digitalWrite(8, HIGH);
delayMicroseconds(100); // Approximately 10% duty cycle @ 765 Hz
digitalWrite(8, LOW);
delayMicroseconds(50);
digitalWrite(9, HIGH);
delayMicroseconds(100); // Approximately 10% duty cycle @ 765 Hz
digitalWrite(9, LOW);
delayMicroseconds(50);
digitalWrite(10, HIGH);
delayMicroseconds(100); // Approximately 10% duty cycle @ 765 Hz
digitalWrite(10, LOW);
delayMicroseconds(50);
}

473 Hz and 8-9% duty cycle

void setup()
{
pinMode(3, OUTPUT);
pinMode(4, OUTPUT);
pinMode(5, OUTPUT);
pinMode(6, OUTPUT);
pinMode(7, OUTPUT);
pinMode(8, OUTPUT);
pinMode(9, OUTPUT);
pinMode(10, OUTPUT);
}

void loop()
{
digitalWrite(3, HIGH);
delayMicroseconds(200); // Approximately 10% duty cycle @ 473 Hz
digitalWrite(3, LOW);
delayMicroseconds(50);
digitalWrite(4, HIGH);
delayMicroseconds(200); // Approximately 10% duty cycle @ 473 Hz
digitalWrite(4, LOW);
delayMicroseconds(50);
digitalWrite(5, HIGH);
delayMicroseconds(200); // Approximately 10% duty cycle @ 473 Hz
digitalWrite(5, LOW);
delayMicroseconds(50);
digitalWrite(6, HIGH);
delayMicroseconds(200); // Approximately 10% duty cycle @ 473 Hz
digitalWrite(6, LOW);
delayMicroseconds(50);
digitalWrite(7, HIGH);
delayMicroseconds(200); // Approximately 10% duty cycle @ 473 Hz
digitalWrite(7, LOW);
delayMicroseconds(50);
digitalWrite(8, HIGH);
delayMicroseconds(200); // Approximately 10% duty cycle @ 473 Hz
digitalWrite(8, LOW);
delayMicroseconds(50);
digitalWrite(9, HIGH);
delayMicroseconds(200); // Approximately 10% duty cycle @ 473 Hz
digitalWrite(9, LOW);
delayMicroseconds(50);
digitalWrite(10, HIGH);
delayMicroseconds(200); // Approximately 10% duty cycle @ 473 Hz
digitalWrite(10, LOW);
delayMicroseconds(50);
}

400 Hz and 8=9% duty cycle

void setup()
{
pinMode(3, OUTPUT);
pinMode(4, OUTPUT);
pinMode(5, OUTPUT);
pinMode(6, OUTPUT);
pinMode(7, OUTPUT);
pinMode(8, OUTPUT);
pinMode(9, OUTPUT);
pinMode(10, OUTPUT);
}

void loop()
{
digitalWrite(3, HIGH);
delayMicroseconds(100); // Approximately 10% duty cycle @ 400 Hz
digitalWrite(3, LOW);
delayMicroseconds(50);
digitalWrite(4, HIGH);
delayMicroseconds(100); // Approximately 10% duty cycle @ 400 Hz
digitalWrite(4, LOW);
delayMicroseconds(50);
digitalWrite(5, HIGH);
delayMicroseconds(100); // Approximately 10% duty cycle @ 400 Hz
digitalWrite(5, LOW);
delayMicroseconds(50);
digitalWrite(6, HIGH);
delayMicroseconds(100); // Approximately 10% duty cycle @ 400 Hz
digitalWrite(6, LOW);
delayMicroseconds(50);
digitalWrite(7, HIGH);
delayMicroseconds(100); // Approximately 10% duty cycle @ 400 Hz
digitalWrite(7, LOW);
delayMicroseconds(50);
digitalWrite(8, HIGH);
delayMicroseconds(100); // Approximately 10% duty cycle @ 400 Hz
digitalWrite(8, LOW);
delayMicroseconds(50);
digitalWrite(9, HIGH);
delayMicroseconds(100); // Approximately 10% duty cycle @ 400 Hz
digitalWrite(9, LOW);
delayMicroseconds(50);
digitalWrite(10, HIGH);
delayMicroseconds(100); // Approximately 10% duty cycle @ 400 Hz
digitalWrite(10, LOW);
delayMicroseconds(50);
}