The data sheet specifies a max current of 110mA at 3V, and a nominal 12 Ohm resistance. You don't specify the base drive voltage, I assume that it is 5V, which should be OK
All of the voltage drop will be across the 1K resistor in the collector of the transistor.
There is a discrepancy between the the resistance and current consumption in the data sheets for the buzzer, the resistance is probably the DC component, at 4kHz it appears to draw less current, so there is a significant reactive component. You need a resistor of around 15 to 20 Ohms in series(with a suitable power rating), rather than 1K, and you need to check that the voltage does not exceed 4 Volts across the buzzer in use.
Incidentally, without a sound level meter you will have no way of check it is up to spec, you just have to rely on the data sheets,
cheers,
Richard
