Hi, Symptoms of brain tumors can vary. Abnormal smell are very nonspecific and can be caused by many causes including congestion, sinusitis and allergies. Abnormal smells in neurological disorders are best described in temporal lobe seizures which can be caused by brain tumors. However, there are other signs that can occur with brain tumors. Headache being the most common which is typically positional (worse when lying down and in the morning), vision changes, worsening balance, problems with speech, weakness, numbness and tingling.It really depends on where the tumor is. A crackling in the head is unlikely to be related to any sort of tumor. Such a sounds could come from the neck or ears for instance. If you are very concerned you can see a neurologist and have them do a thorough exam on your to see if there is anything abnormal. The gold standard for diagnosis is an MRI and if present then a biopsy, but I think it s highly unlikely that you have one. Hope I have answered your query. Let me know if I can assist you further. Regards, Dr. Janne Nissinen, Neurologist