The perception of your chest voice and head voice sounding the same could be due to a few reasons:
Lack of Vocal Technique: Chest voice and head voice are distinct registers in the human voice. Chest voice typically refers to the lower and richer register, while head voice refers to the higher and lighter register. If you are perceiving both registers to sound the same, it might indicate that you haven't developed proper vocal technique or haven't explored the full range and capabilities of your voice. Working with a vocal coach or voice instructor who specializes in technique can help you differentiate and develop control over these registers.
Unbalanced Resonance: Resonance is the way sound vibrations resonate within the vocal tract. The perception of chest voice and head voice can be influenced by how your vocal resonators (chest, throat, mouth, nasal cavity) are engaged. If there is an imbalance in how you are utilizing your resonators, it can lead to a lack of distinction between chest and head voice. Developing a balanced resonance through vocal exercises and training can help differentiate the two registers.
Natural Voice Characteristics: It's also worth noting that everyone's voice is unique, and individual voice characteristics can vary. Some individuals naturally have a more blended or less pronounced distinction between chest and head voice. This doesn't necessarily indicate a problem unless it is causing vocal limitations or difficulties in singing or speaking.
Working with a qualified vocal professional, such as a voice teacher or vocal coach, can provide you with personalized guidance and exercises to help you explore and develop your vocal registers, improve vocal technique, and achieve a more balanced and versatile voice. They can also assess your specific vocal characteristics and provide tailored advice.