TC reported loud air discharge sound from TIB1 at Front DT car. TC feedback MR pressure 10 bar. No o ther fault indications. Train performance - ok. ~~~~~ Checked and found 3534 air compressor safety valve blowing at 9.4 bar. Found Domnick Hunter filter choked. Cleaned & serviced filter. Function test found ok . Air compressor cut out at 10.1 bar N.AKHAIR//07.12.21 --------------