Method and apparatus for imparting to headphones the sound-reproducing characteristics of loudspeakers

Claim 2

Method for creating sound signals at the eardrums of a listener by means of earphones, to correspond to sound signals which would be created at said eardrums of said listener in a predetermined acoustical environment in response to first electrical signals applied to a loudspeaker, comprising, in combination, the steps of measuring the amplitude and delay time of soundwaves at said eardrums of said listener as a function of frequency in response to electrical signals applied to said loudspeaker when said listener is in said acoustical environment in such a manner as to determine a corresponding desired transfer function; measuring the amplitude and delay time of soundwaves at said eardrums of said listener as a function of frequency in response to electrical signals applied to said earphones in such a manner as to determine a corresponding earphone transfer function; and furnishing an electrical network having a network transfer function corresponding to the ratio of said desired transfer function to said earphone transfer function, said electrical network having first input for receiving said first electrical signals and a pair of outputs; and connecting said earphones to said pair of outputs.

Claim 3

A method as set forth in claim 1, wherein a predetermined time shift exists between soundwaves produces at said eardrums of said listener by said earphones and the soundwaves which would exist at said eardrums of said listener in said predetermined acoustical environment in response to said first electrical signals.

Claim 4

Arrangement for creating sound signals at the eardrums of a listener to correspond to sound signals which would be created at said eardrums of said listener in response to electrical signals applied to a loudspeakEr positioned symmetrically to said eardrums of said listener, and wherein a transfer function AM(f) defines the sound pressure at said eardrums of said listener in response to predetermined first electrical signals applied to said loudspeaker, comprising, in combination, earphone means for creating an earphone transfer characteristic AK, said earphone transfer characteristic constituting a measure of the variation with respect to frequency of the sound pressure at said eardrums in response to earphone test signals applied to said earphones; network means having at least one input for receiving electrical signals, a pair of outputs, and a network transfer function corresponding to the ratio of AM(f) divided by AK(f); and connecting means for connecting said earphones to said pair of outputs of said network means and said first electrical signals to said input of said network means.

Claim 5

Arrangement for creating sound signals at the eardrums of a listener to correspond to sound signals which would be created at said eardrums of said listener in response to electrical signals applied to a loudspeakEr positioned symmetrically to said eardrums of said listener, and wherein a transfer function AM(f) defines the sound pressure at said eardrums of said listener in response to predetermined first electrical signals applied to said loudspeaker, comprising, in combination, earphone means for creating an earphone transfer characteristic AK, said earphone transfer characteristic constituting a measure of the variation with respect to frequency of the sound pressure at said eardrums in response to earphone test signals applied to said earphones; network means having at least one input for receiving electrical signals, a pair of outputs, and a network transfer function corresponding to the ratio of AM(f) divided by AK(f); and connecting means for connecting said earphones to said pair of outputs of said network means and said first electrical signals to said input of said network means.

Claim 6

An arrangement as set forth in claim 3, wherein said predetermined acoustical environment comprises a first and second loudspeaker positioned symmetrically to said eardrums of said listener and responsive, respectively, to first and second electrical signals; wherein a first and second desired transfer function AC(f) and AS(f) define, respectively, the transfer function from the input of said first loudspeaker to said first and second eardrum of said listener respectively; wherein said network means have a first and second input for, respectively, receiving said first and second electrical signals; wherein said electrical network means comprise a first and second summing stage, each of said summing stages having a first and second input and a summing output; wherein said electrical network means further comprise a first and second input stage having a transfer function substantially equal to AC(f) divided by AS(f) and a first and second output stage having a transfer function substantially equal to AS(f) divided by AK(f); wherein said network means further comprise first connecting means connecting said first input of said network means directly to said first input of said first summing stage, and said second input of said network means directly to said first input of said second summing stage, second connecting means for interconnecting said first input stage between said first input of said network means and said second input of said second summing stage; third connecting means for connecting said second input stage between said second input of said network means and said second input of said first summing stage; and fourth connecting means connecting said first output stage between said summing output of said first summing amplifier and said first output of said network means and for connecting said second output stage between said output of said second summing stage and said second output of said network means.

Claim 7

An arrangement as set forth in claim 4, wherein said predetermined acoustical environment further comprises a third and fourth loudspeaker, arranged symmetrically with respect to said eardrums of said listener; further comprising additional network means, corresponding to said network means set forth in claim 4, and connected to said third and fourth loudspeaker, said additional network means also having a pair of outputs; further comprising a first and second additional summing stage each having a first and second input and an output; further comprising means for connecting one of said pairs of outputs of said first and additional network means respectively to said first and second input of said first additional summing stage, and the other of said outputs of said first and additional network means to said first and second inputs of said second additional summing stage; and means for connecting said first and second earphones respectively to said output of said first and second additional summing stages.