async Action Result does not end

hi I have a requirement in which i am updating the token number i am using SpeechSynthesizer but after the sound play my is not returning it is in blocking mode and never end execution.

public async Task UpdateCounter(Counter counter)
{
using (CounterAppForANTHEntities1 entities = new CounterAppForANTHEntities1())
{
Counter updatedCustomer = (from c in entities.Counters
where c.id == 1
select c).FirstOrDefault();
updatedCustomer.Counter_value = updatedCustomer.Counter_value+1;
Console.Beep(767, 800);
entities.SaveChanges();
SpeechSynthesizer synthesizer = new SpeechSynthesizer();
synthesizer.Rate = 0;
synthesizer.Volume = 100;
int res = updatedCustomer.Counter_value;
string value = "Token Number" + IntToString(res);
//await Task.Delay(3000);
synthesizer.SpeakAsync(value);
return View(updatedCustomer);
// return RedirectToAction("Index");
}
return RedirectToAction("Index");
}