Control AC Load with Voice Commands

String voice;

#define r1 5
int relay1 = LOW;
#define r2 6
int relay2 = LOW;
#define r3 7
int relay3 = LOW;
#define r4 8
int relay4 = LOW;
void setup() 
{                                           
  Serial.begin(9600);
   pinMode(r1, OUTPUT); 
    pinMode(r2, OUTPUT);
    pinMode(r3, OUTPUT); 
    pinMode(r4, OUTPUT);
 }
void loop() {
 while (Serial.available())   //Check if there is an available byte to read
  {                            
  delay(10);                   //Delay added to make thing stable
  char c = Serial.read();      //Conduct a serial read
  voice += c;                  //Shorthand for voice = voice + c
  } 

  if (voice.length() > 0) 
  {
    Serial.println(voice);
   if(voice == "all off")                             
     {
            digitalWrite(r1,0);
            digitalWrite(r2,0);  //all off
            digitalWrite(r3,0);
            digitalWrite(r4,0);
            delay(250);
     }  
  else if(voice == "fan")                              
     {
    
            relay1 = ~ relay1;
            digitalWrite(r1,relay1);
            delay(250);
     }
  else if(voice == "light")                              
     {
            relay2 = ~ relay2;
            digitalWrite(r2,relay2);
            delay(250);
     }
  else if(voice == "lamp")                              
     {
            relay3 = ~ relay3;
            digitalWrite(r3,relay3);
            delay(250);
     }
      else if(voice == "tubelight")                              
     {
             relay4 = ~ relay4;
            digitalWrite(r4,relay4);
            delay(250);
     }
  voice="";                                                       //Reset the variable after initiating
  }}