_vector_13 error message

I am trying to use a range finder and come back with a tone depending on the distance. This is the code that I am using:

#include <NewPing.h>

#define TRIGGER_PIN 12 // Arduino pin tied to trigger pin on the ultrasonic sensor.
#define ECHO_PIN 11 // Arduino pin tied to echo pin on the ultrasonic sensor.
#define MAX_DISTANCE 200 // Maximum distance we want to ping for (in centimeters). Maximum sensor distance is rated at 400-500cm.

NewPing sonar(TRIGGER_PIN, ECHO_PIN, MAX_DISTANCE); // NewPing setup of pins and maximum distance.

void setup() {
Serial.begin(115200); // Open serial monitor at 115200 baud to see ping results.
}

void loop() {
delay(50); // Wait 50ms between pings (about 20 pings/sec). 29ms should be the shortest delay between pings.
unsigned int uS = sonar.ping(); // Send ping, get ping time in microseconds (uS).
Serial.print("Ping: ");
Serial.print(uS / US_ROUNDTRIP_CM); // Convert ping time to distance in cm and print result (0 = outside set distance range)
Serial.println(“cm”);
// play a note on pin 7 for 10 ms:
int y=uS / US_ROUNDTRIP_CM;
int z=2000/y;
tone(8, z, 10);

I am new at this so excuse any lack of basic knowledge but I get this error message:

C:\Users*****\AppData\Local\Temp\build2945468678791214849.tmp/core.a(Tone.cpp.o): In function __vector_13': C:\Program Files (x86)\Arduino\hardware\arduino\avr\cores\arduino/Tone.cpp:538: multiple definition of __vector_13’
NewPing\NewPing.cpp.o:C:\Program Files (x86)\Arduino\libraries\NewPing/NewPing.cpp:214: first defined here
c:/program files (x86)/arduino/hardware/tools/avr/bin/…/lib/gcc/avr/4.8.1/…/…/…/…/avr/bin/ld.exe: Disabling relaxation: it will not work with multiple definitions
collect2.exe: error: ld returned 1 exit status
Error compiling.

Displaying the distance works well but I need to make it audibe. What should i be doing?

Thanks

PS (***** is replacing my name in C:\users)

Download and install the NewTone library (and use it), by the same author of NewPing (NewPing and Tone have timer conflicts - which is why your compile is failing).