You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Outcome", "Participant", "Intervention"].

Please return the output as a JSON object of the format: {"Participant" : ["patients with COPD", ...], "Intervention" : ["Atenolol", ...], "Outcome" : ["blood pressure", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Effects of two-month vocal exercising with and without spectral biofeedback on student actors ' speaking voice . Twelve student actors ( 6 males , 6 females ) were given voice training for two months . Randomly selected , half of the students ( 3 males , 3 females ) was trained in the traditional way , while the other half was given biofeedback with real-time spectrum analysis . The aim was a ringing voice quality with strong overtones at 3-5 kHz . Text samples read at different loudness levels were recorded before and after training . Fundamental frequency ( F0 ) , sound pressure level ( SPL ) and long-term-average spectrum ( LTAS ) analyses were made . Voice quality was evaluated by two voice trainers . Sound energy at 3-5 kHz increased by 3-4 dB ( 1.5-14.5 dB ) across groups after training . This change , which was slightly larger for the biofeedback ( BF ) group , did not correlate with SPL . F0 increased slightly in the BF group and decreased in the control group . The relative dB level of fundamental decreased significantly more in the BF group probably suggesting a tighter adduction . Voice quality improved in both groups . Visual feedback seems to add some efficacy in voice training . However , there is a danger of hyperfunctional voice production if other sensory feedback is neglected .
{"Intervention": ["voice training", "spectral biofeedback", "two-month vocal exercising", "traditional way"], "Outcome": ["long-term-average spectrum ( LTAS ) analyses", "efficacy", "Fundamental frequency ( F0 ) , sound pressure level ( SPL )", "F0", "Voice quality", "SPL", "Sound energy at 3-5 kHz", "ringing voice quality with strong overtones at 3-5 kHz", "relative dB level of fundamental"], "Participant": ["( 6 males , 6 females )"]}